diff --git a/.github/ISSUE_TEMPLATE/bug_report.yml b/.github/ISSUE_TEMPLATE/bug_report.yml
new file mode 100644
index 00000000..9cda2b44
--- /dev/null
+++ b/.github/ISSUE_TEMPLATE/bug_report.yml
@@ -0,0 +1,56 @@
+name: Bug report
+description: Report a reproducible UnitFlow problem
+title: "bug: "
+labels: [bug]
+body:
+  - type: markdown
+    attributes:
+      value: Thanks for helping improve UnitFlow. Remove private information before submitting logs or screenshots.
+  - type: textarea
+    id: summary
+    attributes:
+      label: What happened?
+      description: Describe the problem and what you expected instead.
+    validations:
+      required: true
+  - type: input
+    id: version
+    attributes:
+      label: UnitFlow version or commit
+    validations:
+      required: true
+  - type: input
+    id: platform
+    attributes:
+      label: Platform and OS
+    validations:
+      required: true
+  - type: textarea
+    id: steps
+    attributes:
+      label: Steps to reproduce
+      placeholder: |
+        1. Select ...
+        2. Enter ...
+        3. Observe ...
+    validations:
+      required: true
+  - type: textarea
+    id: conversion
+    attributes:
+      label: Conversion details
+      description: Include source unit, destination unit, input, actual output, and expected output when relevant.
+  - type: textarea
+    id: logs
+    attributes:
+      label: Logs or screenshots
+      description: Optional. Remove secrets and personal information.
+  - type: checkboxes
+    id: checks
+    attributes:
+      label: Checks
+      options:
+        - label: I searched existing issues for duplicates.
+          required: true
+        - label: I removed secrets and private information.
+          required: true
diff --git a/.github/ISSUE_TEMPLATE/feature_request.yml b/.github/ISSUE_TEMPLATE/feature_request.yml
new file mode 100644
index 00000000..4be21714
--- /dev/null
+++ b/.github/ISSUE_TEMPLATE/feature_request.yml
@@ -0,0 +1,45 @@
+name: Feature request
+description: Suggest an improvement for UnitFlow
+title: "feat: "
+labels: [enhancement]
+body:
+  - type: textarea
+    id: problem
+    attributes:
+      label: Problem or opportunity
+      description: What user need would this solve?
+    validations:
+      required: true
+  - type: textarea
+    id: proposal
+    attributes:
+      label: Proposed solution
+      description: Describe the behavior, UI, units, or workflow you would like.
+    validations:
+      required: true
+  - type: textarea
+    id: alternatives
+    attributes:
+      label: Alternatives considered
+      description: Optional alternatives or tradeoffs.
+  - type: dropdown
+    id: area
+    attributes:
+      label: Area
+      options:
+        - Rust core
+        - Flutter UI
+        - Unit catalog
+        - Accessibility
+        - Documentation
+        - Build and release
+        - Other
+    validations:
+      required: true
+  - type: checkboxes
+    id: checks
+    attributes:
+      label: Checks
+      options:
+        - label: I searched existing issues for similar requests.
+          required: true
diff --git a/.github/pull_request_template.md b/.github/pull_request_template.md
new file mode 100644
index 00000000..fc077559
--- /dev/null
+++ b/.github/pull_request_template.md
@@ -0,0 +1,21 @@
+## Summary
+
+Describe the problem and the focused change that solves it.
+
+## Validation
+
+- [ ] Rust checks/tests pass when Rust code changed.
+- [ ] Flutter analyze/tests pass when Flutter code changed.
+- [ ] Conversion constants/formulas have regression coverage when changed.
+- [ ] UI changes were checked on narrow and wide layouts.
+- [ ] Accessibility implications were reviewed.
+- [ ] Documentation/changelog were updated when needed.
+- [ ] No secrets or private information are included.
+
+## Screenshots
+
+Add screenshots for meaningful UI changes when useful.
+
+## Notes / limitations
+
+Call out migrations, compatibility concerns, follow-up work, or known limitations.
diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
new file mode 100644
index 00000000..cabc01a4
--- /dev/null
+++ b/.github/workflows/ci.yml
@@ -0,0 +1,52 @@
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
+permissions:
+  contents: read
+
+jobs:
+  rust:
+    name: Rust core
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install Rust
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Cargo check
+        run: cargo check --workspace --all-targets
+
+      - name: Cargo test
+        run: cargo test --workspace
+
+  flutter:
+    name: Flutter app
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install Flutter
+        uses: subosito/flutter-action@v2
+        with:
+          channel: stable
+          cache: true
+
+      - name: Resolve packages
+        working-directory: app
+        run: flutter pub get
+
+      - name: Analyze
+        working-directory: app
+        run: flutter analyze
+
+      - name: Test
+        working-directory: app
+        run: flutter test
diff --git a/app/analysis_options.yaml b/app/analysis_options.yaml
new file mode 100644
index 00000000..a59810ec
--- /dev/null
+++ b/app/analysis_options.yaml
@@ -0,0 +1,19 @@
+analyzer:
+  language:
+    strict-casts: true
+    strict-inference: true
+    strict-raw-types: true
+  errors:
+    dead_code: error
+    unused_import: error
+    unused_local_variable: error
+    invalid_assignment: error
+
+linter:
+  rules:
+    - always_declare_return_types
+    - avoid_print
+    - avoid_relative_lib_imports
+    - cancel_subscriptions
+    - directives_ordering
+    - use_build_context_synchronously
diff --git a/app/lib/core/converter.dart b/app/lib/core/converter.dart
new file mode 100644
index 00000000..ff8f5f99
--- /dev/null
+++ b/app/lib/core/converter.dart
@@ -0,0 +1,92 @@
+import 'dart:math' as math;
+
+import 'unit_model.dart';
+
+class ConversionException implements Exception {
+  const ConversionException(this.message);
+
+  final String message;
+
+  @override
+  String toString() => message;
+}
+
+class Converter {
+  const Converter();
+
+  double convert({
+    required double value,
+    required ConversionUnit from,
+    required ConversionUnit to,
+  }) {
+    if (from.category != to.category) {
+      throw const ConversionException('Units must belong to the same category.');
+    }
+
+    if (from.category == UnitCategory.temperature) {
+      return _convertTemperature(value, from.id, to.id);
+    }
+
+    if (to.factorToBase == 0) {
+      throw const ConversionException('Destination unit has an invalid zero factor.');
+    }
+
+    return value * from.factorToBase / to.factorToBase;
+  }
+
+  List<double> batchConvert({
+    required Iterable<double> values,
+    required ConversionUnit from,
+    required ConversionUnit to,
+  }) {
+    return values
+        .map((double value) => convert(value: value, from: from, to: to))
+        .toList(growable: false);
+  }
+
+  String format(
+    double value, {
+    int decimalPlaces = 8,
+    bool scientific = false,
+  }) {
+    final int safePlaces = decimalPlaces.clamp(0, 15).toInt();
+    if (value.isNaN || value.isInfinite) {
+      return value.toString();
+    }
+    if (scientific) {
+      return value.toStringAsExponential(safePlaces);
+    }
+
+    final String fixed = value.toStringAsFixed(safePlaces);
+    if (!fixed.contains('.')) {
+      return fixed;
+    }
+    return fixed.replaceFirst(RegExp(r'\.?0+$'), '');
+  }
+
+  double round(double value, int decimalPlaces) {
+    final int safePlaces = decimalPlaces.clamp(0, 15).toInt();
+    final double scale = math.pow(10, safePlaces).toDouble();
+    return (value * scale).roundToDouble() / scale;
+  }
+
+  double _convertTemperature(double value, String from, String to) {
+    if (from == to) {
+      return value;
+    }
+
+    final double kelvin = switch (from) {
+      'kelvin' => value,
+      'celsius' => value + 273.15,
+      'fahrenheit' => (value + 459.67) * 5 / 9,
+      _ => throw ConversionException('Unknown temperature unit: $from'),
+    };
+
+    return switch (to) {
+      'kelvin' => kelvin,
+      'celsius' => kelvin - 273.15,
+      'fahrenheit' => kelvin * 9 / 5 - 459.67,
+      _ => throw ConversionException('Unknown temperature unit: $to'),
+    };
+  }
+}
diff --git a/app/lib/core/unit_catalog.dart b/app/lib/core/unit_catalog.dart
new file mode 100644
index 00000000..3413ca6b
--- /dev/null
+++ b/app/lib/core/unit_catalog.dart
@@ -0,0 +1,93 @@
+import 'unit_model.dart';
+
+const List<ConversionUnit> unitCatalog = <ConversionUnit>[
+  ConversionUnit(id: 'meter', category: UnitCategory.length, name: 'Meter', symbol: 'm', factorToBase: 1, aliases: <String>['metre'], description: 'SI base unit of length.'),
+  ConversionUnit(id: 'kilometer', category: UnitCategory.length, name: 'Kilometer', symbol: 'km', factorToBase: 1000, aliases: <String>['kilometre'], description: 'One thousand meters.'),
+  ConversionUnit(id: 'centimeter', category: UnitCategory.length, name: 'Centimeter', symbol: 'cm', factorToBase: 0.01, description: 'One hundredth of a meter.'),
+  ConversionUnit(id: 'millimeter', category: UnitCategory.length, name: 'Millimeter', symbol: 'mm', factorToBase: 0.001, description: 'One thousandth of a meter.'),
+  ConversionUnit(id: 'inch', category: UnitCategory.length, name: 'Inch', symbol: 'in', factorToBase: 0.0254, aliases: <String>['inches'], description: 'Exactly 2.54 centimeters.'),
+  ConversionUnit(id: 'foot', category: UnitCategory.length, name: 'Foot', symbol: 'ft', factorToBase: 0.3048, aliases: <String>['feet'], description: 'Twelve inches.'),
+  ConversionUnit(id: 'yard', category: UnitCategory.length, name: 'Yard', symbol: 'yd', factorToBase: 0.9144, description: 'Three feet.'),
+  ConversionUnit(id: 'mile', category: UnitCategory.length, name: 'Mile', symbol: 'mi', factorToBase: 1609.344, description: '5,280 feet.'),
+  ConversionUnit(id: 'nautical_mile', category: UnitCategory.length, name: 'Nautical mile', symbol: 'nmi', factorToBase: 1852, description: 'International nautical mile.'),
+
+  ConversionUnit(id: 'kilogram', category: UnitCategory.mass, name: 'Kilogram', symbol: 'kg', factorToBase: 1, description: 'SI base unit of mass.'),
+  ConversionUnit(id: 'gram', category: UnitCategory.mass, name: 'Gram', symbol: 'g', factorToBase: 0.001, description: 'One thousandth of a kilogram.'),
+  ConversionUnit(id: 'milligram', category: UnitCategory.mass, name: 'Milligram', symbol: 'mg', factorToBase: 0.000001, description: 'One millionth of a kilogram.'),
+  ConversionUnit(id: 'tonne', category: UnitCategory.mass, name: 'Metric tonne', symbol: 't', factorToBase: 1000, aliases: <String>['metric ton'], description: 'One thousand kilograms.'),
+  ConversionUnit(id: 'ounce', category: UnitCategory.mass, name: 'Ounce', symbol: 'oz', factorToBase: 0.028349523125, description: 'International avoirdupois ounce.'),
+  ConversionUnit(id: 'pound', category: UnitCategory.mass, name: 'Pound', symbol: 'lb', factorToBase: 0.45359237, aliases: <String>['lbs'], description: 'International avoirdupois pound.'),
+
+  ConversionUnit(id: 'kelvin', category: UnitCategory.temperature, name: 'Kelvin', symbol: 'K', factorToBase: 1, description: 'SI base unit of thermodynamic temperature.'),
+  ConversionUnit(id: 'celsius', category: UnitCategory.temperature, name: 'Celsius', symbol: '°C', factorToBase: 1, aliases: <String>['centigrade'], description: 'Temperature scale offset from kelvin by 273.15.'),
+  ConversionUnit(id: 'fahrenheit', category: UnitCategory.temperature, name: 'Fahrenheit', symbol: '°F', factorToBase: 1, description: 'Fahrenheit temperature scale.'),
+
+  ConversionUnit(id: 'second', category: UnitCategory.time, name: 'Second', symbol: 's', factorToBase: 1, description: 'SI base unit of time.'),
+  ConversionUnit(id: 'millisecond', category: UnitCategory.time, name: 'Millisecond', symbol: 'ms', factorToBase: 0.001, description: 'One thousandth of a second.'),
+  ConversionUnit(id: 'minute', category: UnitCategory.time, name: 'Minute', symbol: 'min', factorToBase: 60, description: 'Sixty seconds.'),
+  ConversionUnit(id: 'hour', category: UnitCategory.time, name: 'Hour', symbol: 'h', factorToBase: 3600, description: 'Sixty minutes.'),
+  ConversionUnit(id: 'day', category: UnitCategory.time, name: 'Day', symbol: 'd', factorToBase: 86400, description: 'Twenty-four hours.'),
+  ConversionUnit(id: 'week', category: UnitCategory.time, name: 'Week', symbol: 'wk', factorToBase: 604800, description: 'Seven days.'),
+
+  ConversionUnit(id: 'square_meter', category: UnitCategory.area, name: 'Square meter', symbol: 'm²', factorToBase: 1, aliases: <String>['sqm'], description: 'Area of a one-meter square.'),
+  ConversionUnit(id: 'square_kilometer', category: UnitCategory.area, name: 'Square kilometer', symbol: 'km²', factorToBase: 1000000, description: 'One million square meters.'),
+  ConversionUnit(id: 'square_foot', category: UnitCategory.area, name: 'Square foot', symbol: 'ft²', factorToBase: 0.09290304, aliases: <String>['sq ft'], description: 'Area of a one-foot square.'),
+  ConversionUnit(id: 'acre', category: UnitCategory.area, name: 'Acre', symbol: 'ac', factorToBase: 4046.8564224, description: '43,560 square feet.'),
+  ConversionUnit(id: 'hectare', category: UnitCategory.area, name: 'Hectare', symbol: 'ha', factorToBase: 10000, description: 'Ten thousand square meters.'),
+
+  ConversionUnit(id: 'liter', category: UnitCategory.volume, name: 'Liter', symbol: 'L', factorToBase: 1, aliases: <String>['litre'], description: 'Metric unit of volume.'),
+  ConversionUnit(id: 'milliliter', category: UnitCategory.volume, name: 'Milliliter', symbol: 'mL', factorToBase: 0.001, aliases: <String>['ml'], description: 'One thousandth of a liter.'),
+  ConversionUnit(id: 'cubic_meter', category: UnitCategory.volume, name: 'Cubic meter', symbol: 'm³', factorToBase: 1000, description: 'One thousand liters.'),
+  ConversionUnit(id: 'us_teaspoon', category: UnitCategory.volume, name: 'US teaspoon', symbol: 'tsp', factorToBase: 0.00492892159375, description: 'US customary teaspoon.'),
+  ConversionUnit(id: 'us_tablespoon', category: UnitCategory.volume, name: 'US tablespoon', symbol: 'tbsp', factorToBase: 0.01478676478125, description: 'US customary tablespoon.'),
+  ConversionUnit(id: 'us_cup', category: UnitCategory.volume, name: 'US cup', symbol: 'cup', factorToBase: 0.2365882365, description: 'US customary cup.'),
+  ConversionUnit(id: 'us_gallon', category: UnitCategory.volume, name: 'US gallon', symbol: 'gal', factorToBase: 3.785411784, description: 'US customary liquid gallon.'),
+
+  ConversionUnit(id: 'meter_per_second', category: UnitCategory.speed, name: 'Meter per second', symbol: 'm/s', factorToBase: 1, aliases: <String>['mps'], description: 'SI derived unit of speed.'),
+  ConversionUnit(id: 'kilometer_per_hour', category: UnitCategory.speed, name: 'Kilometer per hour', symbol: 'km/h', factorToBase: 1 / 3.6, aliases: <String>['kph', 'kmph'], description: 'Kilometers traveled in one hour.'),
+  ConversionUnit(id: 'mile_per_hour', category: UnitCategory.speed, name: 'Mile per hour', symbol: 'mph', factorToBase: 0.44704, description: 'Miles traveled in one hour.'),
+  ConversionUnit(id: 'knot', category: UnitCategory.speed, name: 'Knot', symbol: 'kn', factorToBase: 1852 / 3600, aliases: <String>['kt'], description: 'One nautical mile per hour.'),
+
+  ConversionUnit(id: 'byte', category: UnitCategory.data, name: 'Byte', symbol: 'B', factorToBase: 1, description: 'Eight bits.'),
+  ConversionUnit(id: 'bit', category: UnitCategory.data, name: 'Bit', symbol: 'bit', factorToBase: 0.125, description: 'One eighth of a byte.'),
+  ConversionUnit(id: 'kilobyte', category: UnitCategory.data, name: 'Kilobyte', symbol: 'kB', factorToBase: 1000, description: 'One thousand bytes.'),
+  ConversionUnit(id: 'megabyte', category: UnitCategory.data, name: 'Megabyte', symbol: 'MB', factorToBase: 1000000, description: 'One million bytes.'),
+  ConversionUnit(id: 'gigabyte', category: UnitCategory.data, name: 'Gigabyte', symbol: 'GB', factorToBase: 1000000000, description: 'One billion bytes.'),
+  ConversionUnit(id: 'kibibyte', category: UnitCategory.data, name: 'Kibibyte', symbol: 'KiB', factorToBase: 1024, description: '1,024 bytes.'),
+  ConversionUnit(id: 'mebibyte', category: UnitCategory.data, name: 'Mebibyte', symbol: 'MiB', factorToBase: 1048576, description: '1,048,576 bytes.'),
+
+  ConversionUnit(id: 'pascal', category: UnitCategory.pressure, name: 'Pascal', symbol: 'Pa', factorToBase: 1, description: 'SI derived unit of pressure.'),
+  ConversionUnit(id: 'kilopascal', category: UnitCategory.pressure, name: 'Kilopascal', symbol: 'kPa', factorToBase: 1000, description: 'One thousand pascals.'),
+  ConversionUnit(id: 'bar', category: UnitCategory.pressure, name: 'Bar', symbol: 'bar', factorToBase: 100000, description: 'One hundred kilopascals.'),
+  ConversionUnit(id: 'atmosphere', category: UnitCategory.pressure, name: 'Standard atmosphere', symbol: 'atm', factorToBase: 101325, description: 'Standard atmosphere.'),
+  ConversionUnit(id: 'psi', category: UnitCategory.pressure, name: 'Pound per square inch', symbol: 'psi', factorToBase: 6894.757293168, description: 'Pressure in pounds-force per square inch.'),
+
+  ConversionUnit(id: 'joule', category: UnitCategory.energy, name: 'Joule', symbol: 'J', factorToBase: 1, description: 'SI derived unit of energy.'),
+  ConversionUnit(id: 'kilojoule', category: UnitCategory.energy, name: 'Kilojoule', symbol: 'kJ', factorToBase: 1000, description: 'One thousand joules.'),
+  ConversionUnit(id: 'calorie', category: UnitCategory.energy, name: 'Calorie', symbol: 'cal', factorToBase: 4.184, description: 'Thermochemical calorie.'),
+  ConversionUnit(id: 'kilocalorie', category: UnitCategory.energy, name: 'Kilocalorie', symbol: 'kcal', factorToBase: 4184, aliases: <String>['food calorie'], description: 'One thousand thermochemical calories.'),
+  ConversionUnit(id: 'watt_hour', category: UnitCategory.energy, name: 'Watt-hour', symbol: 'Wh', factorToBase: 3600, description: 'Energy from one watt over one hour.'),
+  ConversionUnit(id: 'kilowatt_hour', category: UnitCategory.energy, name: 'Kilowatt-hour', symbol: 'kWh', factorToBase: 3600000, description: 'Energy from one kilowatt over one hour.'),
+
+  ConversionUnit(id: 'watt', category: UnitCategory.power, name: 'Watt', symbol: 'W', factorToBase: 1, description: 'SI derived unit of power.'),
+  ConversionUnit(id: 'kilowatt', category: UnitCategory.power, name: 'Kilowatt', symbol: 'kW', factorToBase: 1000, description: 'One thousand watts.'),
+  ConversionUnit(id: 'megawatt', category: UnitCategory.power, name: 'Megawatt', symbol: 'MW', factorToBase: 1000000, description: 'One million watts.'),
+  ConversionUnit(id: 'horsepower', category: UnitCategory.power, name: 'Mechanical horsepower', symbol: 'hp', factorToBase: 745.69987158227022, description: 'Mechanical horsepower.'),
+
+  ConversionUnit(id: 'radian', category: UnitCategory.angle, name: 'Radian', symbol: 'rad', factorToBase: 1, description: 'SI derived unit of plane angle.'),
+  ConversionUnit(id: 'degree', category: UnitCategory.angle, name: 'Degree', symbol: '°', factorToBase: 0.017453292519943295, aliases: <String>['deg'], description: 'One 360th of a full turn.'),
+  ConversionUnit(id: 'gradian', category: UnitCategory.angle, name: 'Gradian', symbol: 'gon', factorToBase: 0.015707963267948967, aliases: <String>['grad'], description: 'One 400th of a full turn.'),
+  ConversionUnit(id: 'turn', category: UnitCategory.angle, name: 'Turn', symbol: 'turn', factorToBase: 6.283185307179586, aliases: <String>['revolution', 'rev'], description: 'One full revolution.'),
+];
+
+List<ConversionUnit> unitsForCategory(UnitCategory category) {
+  return unitCatalog
+      .where((ConversionUnit unit) => unit.category == category)
+      .toList(growable: false);
+}
+
+List<ConversionUnit> searchCatalog(String query) {
+  return unitCatalog
+      .where((ConversionUnit unit) => unit.matches(query))
+      .toList(growable: false);
+}
diff --git a/app/lib/core/unit_model.dart b/app/lib/core/unit_model.dart
new file mode 100644
index 00000000..220afa7c
--- /dev/null
+++ b/app/lib/core/unit_model.dart
@@ -0,0 +1,79 @@
+enum UnitCategory {
+  length,
+  mass,
+  temperature,
+  time,
+  area,
+  volume,
+  speed,
+  data,
+  pressure,
+  energy,
+  power,
+  angle,
+}
+
+extension UnitCategoryLabel on UnitCategory {
+  String get label {
+    switch (this) {
+      case UnitCategory.length:
+        return 'Length';
+      case UnitCategory.mass:
+        return 'Mass';
+      case UnitCategory.temperature:
+        return 'Temperature';
+      case UnitCategory.time:
+        return 'Time';
+      case UnitCategory.area:
+        return 'Area';
+      case UnitCategory.volume:
+        return 'Volume';
+      case UnitCategory.speed:
+        return 'Speed';
+      case UnitCategory.data:
+        return 'Data';
+      case UnitCategory.pressure:
+        return 'Pressure';
+      case UnitCategory.energy:
+        return 'Energy';
+      case UnitCategory.power:
+        return 'Power';
+      case UnitCategory.angle:
+        return 'Angle';
+    }
+  }
+}
+
+class ConversionUnit {
+  const ConversionUnit({
+    required this.id,
+    required this.category,
+    required this.name,
+    required this.symbol,
+    required this.factorToBase,
+    required this.description,
+    this.aliases = const <String>[],
+  });
+
+  final String id;
+  final UnitCategory category;
+  final String name;
+  final String symbol;
+  final double factorToBase;
+  final String description;
+  final List<String> aliases;
+
+  String get displayName => '$name ($symbol)';
+
+  bool matches(String query) {
+    final String needle = query.trim().toLowerCase();
+    if (needle.isEmpty) {
+      return true;
+    }
+    return id.toLowerCase().contains(needle) ||
+        name.toLowerCase().contains(needle) ||
+        symbol.toLowerCase().contains(needle) ||
+        description.toLowerCase().contains(needle) ||
+        aliases.any((String value) => value.toLowerCase().contains(needle));
+  }
+}
diff --git a/app/lib/main.dart b/app/lib/main.dart
new file mode 100644
index 00000000..5ed2d3d5
--- /dev/null
+++ b/app/lib/main.dart
@@ -0,0 +1,44 @@
+import 'package:flutter/material.dart';
+
+import 'screens/home_screen.dart';
+
+void main() {
+  runApp(const UnitFlowApp());
+}
+
+class UnitFlowApp extends StatelessWidget {
+  const UnitFlowApp({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    final ColorScheme lightScheme = ColorScheme.fromSeed(
+      seedColor: const Color(0xFF3657C8),
+      brightness: Brightness.light,
+    );
+    final ColorScheme darkScheme = ColorScheme.fromSeed(
+      seedColor: const Color(0xFF9EB0FF),
+      brightness: Brightness.dark,
+    );
+
+    return MaterialApp(
+      title: 'UnitFlow',
+      debugShowCheckedModeBanner: false,
+      themeMode: ThemeMode.system,
+      theme: ThemeData(
+        useMaterial3: true,
+        colorScheme: lightScheme,
+        inputDecorationTheme: const InputDecorationTheme(
+          border: OutlineInputBorder(),
+        ),
+      ),
+      darkTheme: ThemeData(
+        useMaterial3: true,
+        colorScheme: darkScheme,
+        inputDecorationTheme: const InputDecorationTheme(
+          border: OutlineInputBorder(),
+        ),
+      ),
+      home: const HomeScreen(),
+    );
+  }
+}
diff --git a/app/lib/screens/home_screen.dart b/app/lib/screens/home_screen.dart
new file mode 100644
index 00000000..7b8d2706
--- /dev/null
+++ b/app/lib/screens/home_screen.dart
@@ -0,0 +1,194 @@
+import 'package:flutter/material.dart';
+
+import '../core/unit_model.dart';
+import '../state/app_state.dart';
+import '../widgets/converter_card.dart';
+import '../widgets/history_section.dart';
+
+class HomeScreen extends StatefulWidget {
+  const HomeScreen({super.key});
+
+  @override
+  State<HomeScreen> createState() => _HomeScreenState();
+}
+
+class _HomeScreenState extends State<HomeScreen> {
+  late final AppState _state;
+  late final TextEditingController _inputController;
+
+  @override
+  void initState() {
+    super.initState();
+    _state = AppState();
+    _inputController = TextEditingController(text: _state.input);
+  }
+
+  @override
+  void dispose() {
+    _inputController.dispose();
+    _state.dispose();
+    super.dispose();
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return AnimatedBuilder(
+      animation: _state,
+      builder: (BuildContext context, Widget? child) {
+        return Scaffold(
+          appBar: AppBar(
+            title: const Row(
+              mainAxisSize: MainAxisSize.min,
+              children: <Widget>[
+                Icon(Icons.swap_horiz_rounded),
+                SizedBox(width: 10),
+                Text('UnitFlow'),
+              ],
+            ),
+            actions: <Widget>[
+              Padding(
+                padding: const EdgeInsets.only(right: 12),
+                child: Center(
+                  child: Text(
+                    'Made by the Sanskar',
+                    style: Theme.of(context).textTheme.labelMedium,
+                  ),
+                ),
+              ),
+            ],
+          ),
+          body: SafeArea(
+            child: SelectionArea(
+              child: SingleChildScrollView(
+                padding: const EdgeInsets.all(16),
+                child: Center(
+                  child: ConstrainedBox(
+                    constraints: const BoxConstraints(maxWidth: 980),
+                    child: Column(
+                      crossAxisAlignment: CrossAxisAlignment.stretch,
+                      children: <Widget>[
+                        _HeroHeader(state: _state),
+                        const SizedBox(height: 16),
+                        _CategorySelector(state: _state),
+                        const SizedBox(height: 16),
+                        ConverterCard(
+                          state: _state,
+                          inputController: _inputController,
+                        ),
+                        const SizedBox(height: 16),
+                        HistorySection(state: _state),
+                        const SizedBox(height: 28),
+                        const Center(
+                          child: Text(
+                            'Offline-first • Open source • MIT License',
+                            textAlign: TextAlign.center,
+                          ),
+                        ),
+                        const SizedBox(height: 12),
+                      ],
+                    ),
+                  ),
+                ),
+              ),
+            ),
+          ),
+        );
+      },
+    );
+  }
+}
+
+class _HeroHeader extends StatelessWidget {
+  const _HeroHeader({required this.state});
+
+  final AppState state;
+
+  @override
+  Widget build(BuildContext context) {
+    final ThemeData theme = Theme.of(context);
+    return Container(
+      padding: const EdgeInsets.all(24),
+      decoration: BoxDecoration(
+        borderRadius: BorderRadius.circular(24),
+        gradient: LinearGradient(
+          colors: <Color>[
+            theme.colorScheme.primaryContainer,
+            theme.colorScheme.secondaryContainer,
+          ],
+        ),
+      ),
+      child: Column(
+        crossAxisAlignment: CrossAxisAlignment.start,
+        children: <Widget>[
+          Text(
+            'Convert with confidence.',
+            style: theme.textTheme.headlineMedium?.copyWith(
+              fontWeight: FontWeight.w700,
+            ),
+          ),
+          const SizedBox(height: 8),
+          Text(
+            'Fast offline conversions, searchable units, batch tools, favorites, recent history, and educational context.',
+            style: theme.textTheme.bodyLarge,
+          ),
+          const SizedBox(height: 14),
+          Wrap(
+            spacing: 8,
+            runSpacing: 8,
+            children: <Widget>[
+              const Chip(
+                avatar: Icon(Icons.offline_bolt_outlined, size: 18),
+                label: Text('Offline core'),
+              ),
+              Chip(
+                avatar: const Icon(Icons.category_outlined, size: 18),
+                label: Text('${UnitCategory.values.length} categories'),
+              ),
+              Chip(
+                avatar: const Icon(Icons.science_outlined, size: 18),
+                label: Text(state.category.label),
+              ),
+            ],
+          ),
+        ],
+      ),
+    );
+  }
+}
+
+class _CategorySelector extends StatelessWidget {
+  const _CategorySelector({required this.state});
+
+  final AppState state;
+
+  @override
+  Widget build(BuildContext context) {
+    return Card(
+      child: Padding(
+        padding: const EdgeInsets.all(16),
+        child: Column(
+          crossAxisAlignment: CrossAxisAlignment.start,
+          children: <Widget>[
+            Text('Category', style: Theme.of(context).textTheme.titleMedium),
+            const SizedBox(height: 12),
+            Wrap(
+              spacing: 8,
+              runSpacing: 8,
+              children: UnitCategory.values.map((UnitCategory category) {
+                return ChoiceChip(
+                  label: Text(category.label),
+                  selected: state.category == category,
+                  onSelected: (bool selected) {
+                    if (selected) {
+                      state.setCategory(category);
+                    }
+                  },
+                );
+              }).toList(growable: false),
+            ),
+          ],
+        ),
+      ),
+    );
+  }
+}
diff --git a/app/lib/state/app_state.dart b/app/lib/state/app_state.dart
new file mode 100644
index 00000000..9c16f293
--- /dev/null
+++ b/app/lib/state/app_state.dart
@@ -0,0 +1,211 @@
+import 'package:flutter/foundation.dart';
+
+import '../core/converter.dart';
+import '../core/unit_catalog.dart';
+import '../core/unit_model.dart';
+
+@immutable
+class UnitPair {
+  const UnitPair(this.fromId, this.toId);
+
+  final String fromId;
+  final String toId;
+
+  @override
+  bool operator ==(Object other) {
+    return other is UnitPair && other.fromId == fromId && other.toId == toId;
+  }
+
+  @override
+  int get hashCode => Object.hash(fromId, toId);
+}
+
+@immutable
+class ConversionRecord {
+  const ConversionRecord({
+    required this.input,
+    required this.output,
+    required this.from,
+    required this.to,
+  });
+
+  final String input;
+  final String output;
+  final ConversionUnit from;
+  final ConversionUnit to;
+}
+
+class AppState extends ChangeNotifier {
+  AppState({Converter converter = const Converter()}) : _converter = converter {
+    _selectDefaultsForCategory();
+    _recalculate(addToHistory: false);
+  }
+
+  final Converter _converter;
+  UnitCategory _category = UnitCategory.length;
+  late ConversionUnit _from;
+  late ConversionUnit _to;
+  String _input = '1';
+  String _output = '';
+  String? _error;
+  int _decimalPlaces = 8;
+  bool _scientific = false;
+  final Set<UnitPair> _favorites = <UnitPair>{};
+  final List<ConversionRecord> _recent = <ConversionRecord>[];
+
+  UnitCategory get category => _category;
+  ConversionUnit get from => _from;
+  ConversionUnit get to => _to;
+  String get input => _input;
+  String get output => _output;
+  String? get error => _error;
+  int get decimalPlaces => _decimalPlaces;
+  bool get scientific => _scientific;
+  List<ConversionRecord> get recent => List<ConversionRecord>.unmodifiable(_recent);
+  Set<UnitPair> get favorites => Set<UnitPair>.unmodifiable(_favorites);
+  List<ConversionUnit> get availableUnits => unitsForCategory(_category);
+
+  bool get isCurrentPairFavorite => _favorites.contains(UnitPair(_from.id, _to.id));
+
+  void setCategory(UnitCategory value) {
+    if (_category == value) {
+      return;
+    }
+    _category = value;
+    _selectDefaultsForCategory();
+    _recalculate(addToHistory: false);
+    notifyListeners();
+  }
+
+  void setFrom(ConversionUnit value) {
+    if (value.category != _category || value.id == _from.id) {
+      return;
+    }
+    _from = value;
+    _recalculate();
+    notifyListeners();
+  }
+
+  void setTo(ConversionUnit value) {
+    if (value.category != _category || value.id == _to.id) {
+      return;
+    }
+    _to = value;
+    _recalculate();
+    notifyListeners();
+  }
+
+  void swapUnits() {
+    final ConversionUnit previousFrom = _from;
+    _from = _to;
+    _to = previousFrom;
+    if (_output.isNotEmpty && _error == null) {
+      _input = _output;
+    }
+    _recalculate();
+    notifyListeners();
+  }
+
+  void setInput(String value) {
+    _input = value;
+    _recalculate(addToHistory: false);
+    notifyListeners();
+  }
+
+  void commitInput() {
+    _recalculate(addToHistory: true);
+    notifyListeners();
+  }
+
+  void setDecimalPlaces(int value) {
+    final int clamped = value.clamp(0, 15).toInt();
+    if (_decimalPlaces == clamped) {
+      return;
+    }
+    _decimalPlaces = clamped;
+    _recalculate(addToHistory: false);
+    notifyListeners();
+  }
+
+  void setScientific(bool value) {
+    if (_scientific == value) {
+      return;
+    }
+    _scientific = value;
+    _recalculate(addToHistory: false);
+    notifyListeners();
+  }
+
+  void toggleCurrentFavorite() {
+    final UnitPair pair = UnitPair(_from.id, _to.id);
+    if (!_favorites.remove(pair)) {
+      _favorites.add(pair);
+    }
+    notifyListeners();
+  }
+
+  List<String> batchConvert(Iterable<String> lines) {
+    final List<String> output = <String>[];
+    for (final String line in lines) {
+      final String trimmed = line.trim();
+      if (trimmed.isEmpty) {
+        continue;
+      }
+      final double? value = double.tryParse(trimmed);
+      if (value == null) {
+        output.add('$trimmed → invalid number');
+        continue;
+      }
+      final double converted = _converter.convert(value: value, from: _from, to: _to);
+      output.add(
+        '$trimmed ${_from.symbol} → ${_converter.format(converted, decimalPlaces: _decimalPlaces, scientific: _scientific)} ${_to.symbol}',
+      );
+    }
+    return output;
+  }
+
+  void clearHistory() {
+    if (_recent.isEmpty) {
+      return;
+    }
+    _recent.clear();
+    notifyListeners();
+  }
+
+  void _selectDefaultsForCategory() {
+    final List<ConversionUnit> units = unitsForCategory(_category);
+    _from = units.first;
+    _to = units.length > 1 ? units[1] : units.first;
+  }
+
+  void _recalculate({bool addToHistory = true}) {
+    final double? value = double.tryParse(_input.trim());
+    if (value == null) {
+      _output = '';
+      _error = _input.trim().isEmpty ? null : 'Enter a valid number.';
+      return;
+    }
+
+    try {
+      final double converted = _converter.convert(value: value, from: _from, to: _to);
+      _output = _converter.format(
+        converted,
+        decimalPlaces: _decimalPlaces,
+        scientific: _scientific,
+      );
+      _error = null;
+      if (addToHistory) {
+        _recent.insert(
+          0,
+          ConversionRecord(input: _input, output: _output, from: _from, to: _to),
+        );
+        if (_recent.length > 12) {
+          _recent.removeRange(12, _recent.length);
+        }
+      }
+    } on ConversionException catch (error) {
+      _output = '';
+      _error = error.message;
+    }
+  }
+}
diff --git a/app/lib/widgets/batch_conversion_dialog.dart b/app/lib/widgets/batch_conversion_dialog.dart
new file mode 100644
index 00000000..3c1d2594
--- /dev/null
+++ b/app/lib/widgets/batch_conversion_dialog.dart
@@ -0,0 +1,85 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+
+import '../state/app_state.dart';
+
+Future<void> showBatchConversionDialog({
+  required BuildContext context,
+  required AppState state,
+}) async {
+  final TextEditingController controller = TextEditingController();
+  List<String> results = const <String>[];
+
+  await showDialog<void>(
+    context: context,
+    builder: (BuildContext context) {
+      return StatefulBuilder(
+        builder: (BuildContext context, StateSetter setState) {
+          return AlertDialog(
+            title: const Text('Batch conversion'),
+            content: SizedBox(
+              width: 620,
+              child: SingleChildScrollView(
+                child: Column(
+                  crossAxisAlignment: CrossAxisAlignment.stretch,
+                  children: <Widget>[
+                    Text(
+                      'Convert multiple values from ${state.from.symbol} to ${state.to.symbol}. Enter one value per line.',
+                    ),
+                    const SizedBox(height: 12),
+                    TextField(
+                      controller: controller,
+                      minLines: 6,
+                      maxLines: 10,
+                      keyboardType: const TextInputType.numberWithOptions(
+                        decimal: true,
+                        signed: true,
+                      ),
+                      decoration: const InputDecoration(
+                        border: OutlineInputBorder(),
+                        hintText: '1\n2.5\n100',
+                      ),
+                    ),
+                    const SizedBox(height: 12),
+                    FilledButton.icon(
+                      onPressed: () {
+                        setState(() {
+                          results = state.batchConvert(controller.text.split('\n'));
+                        });
+                      },
+                      icon: const Icon(Icons.calculate_outlined),
+                      label: const Text('Convert batch'),
+                    ),
+                    if (results.isNotEmpty) ...<Widget>[
+                      const SizedBox(height: 16),
+                      SelectableText(results.join('\n')),
+                    ],
+                  ],
+                ),
+              ),
+            ),
+            actions: <Widget>[
+              if (results.isNotEmpty)
+                TextButton.icon(
+                  onPressed: () {
+                    Clipboard.setData(ClipboardData(text: results.join('\n')));
+                    ScaffoldMessenger.of(context).showSnackBar(
+                      const SnackBar(content: Text('Batch results copied.')),
+                    );
+                  },
+                  icon: const Icon(Icons.copy_outlined),
+                  label: const Text('Copy'),
+                ),
+              TextButton(
+                onPressed: () => Navigator.of(context).pop(),
+                child: const Text('Close'),
+              ),
+            ],
+          );
+        },
+      );
+    },
+  );
+
+  controller.dispose();
+}
diff --git a/app/lib/widgets/converter_card.dart b/app/lib/widgets/converter_card.dart
new file mode 100644
index 00000000..3fb5cde2
--- /dev/null
+++ b/app/lib/widgets/converter_card.dart
@@ -0,0 +1,285 @@
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+
+import '../core/unit_model.dart';
+import '../state/app_state.dart';
+import 'batch_conversion_dialog.dart';
+import 'settings_sheet.dart';
+import 'unit_picker_dialog.dart';
+
+class ConverterCard extends StatelessWidget {
+  const ConverterCard({
+    required this.state,
+    required this.inputController,
+    super.key,
+  });
+
+  final AppState state;
+  final TextEditingController inputController;
+
+  @override
+  Widget build(BuildContext context) {
+    final ThemeData theme = Theme.of(context);
+    final List<ConversionUnit> units = state.availableUnits;
+
+    return Card(
+      clipBehavior: Clip.antiAlias,
+      child: Padding(
+        padding: const EdgeInsets.all(20),
+        child: Column(
+          crossAxisAlignment: CrossAxisAlignment.stretch,
+          children: <Widget>[
+            Row(
+              children: <Widget>[
+                Expanded(
+                  child: Text('Converter', style: theme.textTheme.headlineSmall),
+                ),
+                IconButton(
+                  tooltip: 'Display settings',
+                  onPressed: () => showSettingsSheet(context: context, state: state),
+                  icon: const Icon(Icons.tune),
+                ),
+              ],
+            ),
+            const SizedBox(height: 16),
+            TextField(
+              controller: inputController,
+              keyboardType: const TextInputType.numberWithOptions(
+                decimal: true,
+                signed: true,
+              ),
+              textInputAction: TextInputAction.done,
+              decoration: InputDecoration(
+                labelText: 'Value',
+                errorText: state.error,
+                prefixIcon: const Icon(Icons.pin_outlined),
+                suffixText: state.from.symbol,
+              ),
+              onChanged: state.setInput,
+              onSubmitted: (_) => state.commitInput(),
+            ),
+            const SizedBox(height: 16),
+            LayoutBuilder(
+              builder: (BuildContext context, BoxConstraints constraints) {
+                final bool narrow = constraints.maxWidth < 620;
+                final Widget fromButton = _UnitButton(
+                  label: 'From',
+                  unit: state.from,
+                  onPressed: () => _pickUnit(context, units, true),
+                );
+                final Widget toButton = _UnitButton(
+                  label: 'To',
+                  unit: state.to,
+                  onPressed: () => _pickUnit(context, units, false),
+                );
+                final Widget swap = Semantics(
+                  button: true,
+                  label: 'Swap source and destination units',
+                  child: IconButton.filledTonal(
+                    tooltip: 'Swap units',
+                    onPressed: () {
+                      state.swapUnits();
+                      inputController.text = state.input;
+                      inputController.selection = TextSelection.collapsed(
+                        offset: inputController.text.length,
+                      );
+                    },
+                    icon: Icon(narrow ? Icons.swap_vert : Icons.swap_horiz),
+                  ),
+                );
+
+                if (narrow) {
+                  return Column(
+                    children: <Widget>[
+                      fromButton,
+                      Padding(
+                        padding: const EdgeInsets.symmetric(vertical: 8),
+                        child: swap,
+                      ),
+                      toButton,
+                    ],
+                  );
+                }
+
+                return Row(
+                  children: <Widget>[
+                    Expanded(child: fromButton),
+                    Padding(
+                      padding: const EdgeInsets.symmetric(horizontal: 12),
+                      child: swap,
+                    ),
+                    Expanded(child: toButton),
+                  ],
+                );
+              },
+            ),
+            const SizedBox(height: 20),
+            Container(
+              padding: const EdgeInsets.all(20),
+              decoration: BoxDecoration(
+                borderRadius: BorderRadius.circular(20),
+                color: theme.colorScheme.primaryContainer,
+              ),
+              child: Column(
+                crossAxisAlignment: CrossAxisAlignment.start,
+                children: <Widget>[
+                  Text('Result', style: theme.textTheme.labelLarge),
+                  const SizedBox(height: 6),
+                  SelectableText(
+                    state.output.isEmpty ? '—' : '${state.output} ${state.to.symbol}',
+                    style: theme.textTheme.headlineMedium?.copyWith(
+                      color: theme.colorScheme.onPrimaryContainer,
+                    ),
+                  ),
+                  const SizedBox(height: 12),
+                  Wrap(
+                    spacing: 8,
+                    runSpacing: 8,
+                    children: <Widget>[
+                      FilledButton.tonalIcon(
+                        onPressed: state.output.isEmpty
+                            ? null
+                            : () => _copyResult(context),
+                        icon: const Icon(Icons.copy_outlined),
+                        label: const Text('Copy'),
+                      ),
+                      FilledButton.tonalIcon(
+                        onPressed: state.toggleCurrentFavorite,
+                        icon: Icon(
+                          state.isCurrentPairFavorite
+                              ? Icons.star
+                              : Icons.star_border,
+                        ),
+                        label: Text(
+                          state.isCurrentPairFavorite
+                              ? 'Favorited'
+                              : 'Favorite pair',
+                        ),
+                      ),
+                      FilledButton.tonalIcon(
+                        onPressed: () => showBatchConversionDialog(
+                          context: context,
+                          state: state,
+                        ),
+                        icon: const Icon(Icons.table_rows_outlined),
+                        label: const Text('Batch'),
+                      ),
+                    ],
+                  ),
+                ],
+              ),
+            ),
+            const SizedBox(height: 16),
+            _Explanation(state: state),
+          ],
+        ),
+      ),
+    );
+  }
+
+  Future<void> _pickUnit(
+    BuildContext context,
+    List<ConversionUnit> units,
+    bool pickingFrom,
+  ) async {
+    final ConversionUnit? selected = await showUnitPickerDialog(
+      context: context,
+      title: pickingFrom ? 'Choose source unit' : 'Choose destination unit',
+      units: units,
+      selected: pickingFrom ? state.from : state.to,
+    );
+    if (selected == null) {
+      return;
+    }
+    if (pickingFrom) {
+      state.setFrom(selected);
+    } else {
+      state.setTo(selected);
+    }
+  }
+
+  void _copyResult(BuildContext context) {
+    final String text = '${state.output} ${state.to.symbol}';
+    Clipboard.setData(ClipboardData(text: text));
+    ScaffoldMessenger.of(context).showSnackBar(
+      const SnackBar(content: Text('Result copied.')),
+    );
+  }
+}
+
+class _UnitButton extends StatelessWidget {
+  const _UnitButton({
+    required this.label,
+    required this.unit,
+    required this.onPressed,
+  });
+
+  final String label;
+  final ConversionUnit unit;
+  final VoidCallback onPressed;
+
+  @override
+  Widget build(BuildContext context) {
+    return Semantics(
+      button: true,
+      label: '$label unit: ${unit.name}',
+      child: OutlinedButton(
+        onPressed: onPressed,
+        style: OutlinedButton.styleFrom(
+          padding: const EdgeInsets.symmetric(horizontal: 16, vertical: 16),
+          alignment: Alignment.centerLeft,
+        ),
+        child: Row(
+          children: <Widget>[
+            Expanded(
+              child: Column(
+                crossAxisAlignment: CrossAxisAlignment.start,
+                children: <Widget>[
+                  Text(label, style: Theme.of(context).textTheme.labelMedium),
+                  const SizedBox(height: 4),
+                  Text(unit.displayName, overflow: TextOverflow.ellipsis),
+                ],
+              ),
+            ),
+            const Icon(Icons.expand_more),
+          ],
+        ),
+      ),
+    );
+  }
+}
+
+class _Explanation extends StatelessWidget {
+  const _Explanation({required this.state});
+
+  final AppState state;
+
+  @override
+  Widget build(BuildContext context) {
+    return ExpansionTile(
+      tilePadding: EdgeInsets.zero,
+      title: const Text('How this conversion works'),
+      subtitle: Text('${state.from.name} → ${state.to.name}'),
+      children: <Widget>[
+        Align(
+          alignment: Alignment.centerLeft,
+          child: Text(state.from.description),
+        ),
+        const SizedBox(height: 8),
+        Align(
+          alignment: Alignment.centerLeft,
+          child: Text(state.to.description),
+        ),
+        const SizedBox(height: 8),
+        Align(
+          alignment: Alignment.centerLeft,
+          child: Text(
+            state.category == UnitCategory.temperature
+                ? 'Temperature conversions use an affine scale transformation through kelvin.'
+                : 'Linear conversions pass through the category base unit using each unit factor.',
+          ),
+        ),
+      ],
+    );
+  }
+}
diff --git a/app/lib/widgets/history_section.dart b/app/lib/widgets/history_section.dart
new file mode 100644
index 00000000..3165a02c
--- /dev/null
+++ b/app/lib/widgets/history_section.dart
@@ -0,0 +1,53 @@
+import 'package:flutter/material.dart';
+
+import '../state/app_state.dart';
+
+class HistorySection extends StatelessWidget {
+  const HistorySection({required this.state, super.key});
+
+  final AppState state;
+
+  @override
+  Widget build(BuildContext context) {
+    final List<ConversionRecord> recent = state.recent;
+    if (recent.isEmpty) {
+      return const SizedBox.shrink();
+    }
+
+    return Card(
+      child: Padding(
+        padding: const EdgeInsets.all(16),
+        child: Column(
+          crossAxisAlignment: CrossAxisAlignment.stretch,
+          children: <Widget>[
+            Row(
+              children: <Widget>[
+                Text(
+                  'Recent conversions',
+                  style: Theme.of(context).textTheme.titleMedium,
+                ),
+                const Spacer(),
+                TextButton.icon(
+                  onPressed: state.clearHistory,
+                  icon: const Icon(Icons.delete_sweep_outlined),
+                  label: const Text('Clear'),
+                ),
+              ],
+            ),
+            const SizedBox(height: 8),
+            for (final ConversionRecord record in recent.take(6))
+              ListTile(
+                dense: true,
+                contentPadding: EdgeInsets.zero,
+                leading: const Icon(Icons.history),
+                title: Text(
+                  '${record.input} ${record.from.symbol} → ${record.output} ${record.to.symbol}',
+                ),
+                subtitle: Text('${record.from.name} to ${record.to.name}'),
+              ),
+          ],
+        ),
+      ),
+    );
+  }
+}
diff --git a/app/lib/widgets/settings_sheet.dart b/app/lib/widgets/settings_sheet.dart
new file mode 100644
index 00000000..697c416d
--- /dev/null
+++ b/app/lib/widgets/settings_sheet.dart
@@ -0,0 +1,52 @@
+import 'package:flutter/material.dart';
+
+import '../state/app_state.dart';
+
+Future<void> showSettingsSheet({
+  required BuildContext context,
+  required AppState state,
+}) {
+  return showModalBottomSheet<void>(
+    context: context,
+    showDragHandle: true,
+    builder: (BuildContext context) {
+      return AnimatedBuilder(
+        animation: state,
+        builder: (BuildContext context, Widget? child) {
+          return SafeArea(
+            child: Padding(
+              padding: const EdgeInsets.fromLTRB(24, 4, 24, 28),
+              child: Column(
+                mainAxisSize: MainAxisSize.min,
+                crossAxisAlignment: CrossAxisAlignment.stretch,
+                children: <Widget>[
+                  Text(
+                    'Display settings',
+                    style: Theme.of(context).textTheme.titleLarge,
+                  ),
+                  const SizedBox(height: 20),
+                  Text('Decimal places: ${state.decimalPlaces}'),
+                  Slider(
+                    min: 0,
+                    max: 15,
+                    divisions: 15,
+                    value: state.decimalPlaces.toDouble(),
+                    label: '${state.decimalPlaces}',
+                    onChanged: (double value) => state.setDecimalPlaces(value.round()),
+                  ),
+                  SwitchListTile.adaptive(
+                    contentPadding: EdgeInsets.zero,
+                    title: const Text('Scientific notation'),
+                    subtitle: const Text('Show results using exponential notation.'),
+                    value: state.scientific,
+                    onChanged: state.setScientific,
+                  ),
+                ],
+              ),
+            ),
+          );
+        },
+      );
+    },
+  );
+}
diff --git a/app/lib/widgets/unit_picker_dialog.dart b/app/lib/widgets/unit_picker_dialog.dart
new file mode 100644
index 00000000..e05a4d82
--- /dev/null
+++ b/app/lib/widgets/unit_picker_dialog.dart
@@ -0,0 +1,77 @@
+import 'package:flutter/material.dart';
+
+import '../core/unit_model.dart';
+
+Future<ConversionUnit?> showUnitPickerDialog({
+  required BuildContext context,
+  required String title,
+  required List<ConversionUnit> units,
+  required ConversionUnit selected,
+}) {
+  String query = '';
+
+  return showDialog<ConversionUnit>(
+    context: context,
+    builder: (BuildContext context) {
+      return StatefulBuilder(
+        builder: (BuildContext context, StateSetter setState) {
+          final List<ConversionUnit> filtered = units
+              .where((ConversionUnit unit) => unit.matches(query))
+              .toList(growable: false);
+
+          return AlertDialog(
+            title: Text(title),
+            content: SizedBox(
+              width: 520,
+              height: 520,
+              child: Column(
+                children: <Widget>[
+                  TextField(
+                    autofocus: true,
+                    decoration: const InputDecoration(
+                      prefixIcon: Icon(Icons.search),
+                      labelText: 'Search units',
+                      hintText: 'Name, symbol, alias, or description',
+                    ),
+                    onChanged: (String value) {
+                      setState(() {
+                        query = value;
+                      });
+                    },
+                  ),
+                  const SizedBox(height: 12),
+                  Expanded(
+                    child: filtered.isEmpty
+                        ? const Center(child: Text('No matching units.'))
+                        : ListView.builder(
+                            itemCount: filtered.length,
+                            itemBuilder: (BuildContext context, int index) {
+                              final ConversionUnit unit = filtered[index];
+                              return ListTile(
+                                selected: unit.id == selected.id,
+                                leading: CircleAvatar(child: Text(unit.symbol)),
+                                title: Text(unit.name),
+                                subtitle: Text(unit.description),
+                                trailing: unit.id == selected.id
+                                    ? const Icon(Icons.check_circle)
+                                    : null,
+                                onTap: () => Navigator.of(context).pop(unit),
+                              );
+                            },
+                          ),
+                  ),
+                ],
+              ),
+            ),
+            actions: <Widget>[
+              TextButton(
+                onPressed: () => Navigator.of(context).pop(),
+                child: const Text('Cancel'),
+              ),
+            ],
+          );
+        },
+      );
+    },
+  );
+}
diff --git a/app/pubspec.yaml b/app/pubspec.yaml
new file mode 100644
index 00000000..06289c39
--- /dev/null
+++ b/app/pubspec.yaml
@@ -0,0 +1,20 @@
+name: unitflow
+version: 0.1.0+1
+publish_to: "none"
+description: Offline-first Flutter frontend for the UnitFlow converter.
+
+repository: https://github.com/sanskarIN/unitflow
+
+environment:
+  sdk: ">=3.8.0 <4.0.0"
+
+flutter:
+  uses-material-design: true
+
+dependencies:
+  flutter:
+    sdk: flutter
+
+dev_dependencies:
+  flutter_test:
+    sdk: flutter
diff --git a/app/test/converter_test.dart b/app/test/converter_test.dart
new file mode 100644
index 00000000..3a6080b9
--- /dev/null
+++ b/app/test/converter_test.dart
@@ -0,0 +1,61 @@
+import 'package:flutter_test/flutter_test.dart';
+import 'package:unitflow/core/converter.dart';
+import 'package:unitflow/core/unit_catalog.dart';
+import 'package:unitflow/core/unit_model.dart';
+
+ConversionUnit unit(String id) {
+  return unitCatalog.firstWhere((ConversionUnit value) => value.id == id);
+}
+
+void main() {
+  const Converter converter = Converter();
+
+  test('converts kilometers to meters', () {
+    final double result = converter.convert(
+      value: 1.25,
+      from: unit('kilometer'),
+      to: unit('meter'),
+    );
+    expect(result, closeTo(1250, 1e-12));
+  });
+
+  test('converts Celsius to Fahrenheit', () {
+    final double result = converter.convert(
+      value: 100,
+      from: unit('celsius'),
+      to: unit('fahrenheit'),
+    );
+    expect(result, closeTo(212, 1e-10));
+  });
+
+  test('keeps decimal and binary data units distinct', () {
+    final double decimal = converter.convert(
+      value: 1,
+      from: unit('megabyte'),
+      to: unit('byte'),
+    );
+    final double binary = converter.convert(
+      value: 1,
+      from: unit('mebibyte'),
+      to: unit('byte'),
+    );
+    expect(decimal, 1000000);
+    expect(binary, 1048576);
+  });
+
+  test('rejects mismatched categories', () {
+    expect(
+      () => converter.convert(
+        value: 1,
+        from: unit('meter'),
+        to: unit('kilogram'),
+      ),
+      throwsA(isA<ConversionException>()),
+    );
+  });
+
+  test('formats trailing zeros cleanly', () {
+    expect(converter.format(12.5, decimalPlaces: 6), '12.5');
+    expect(converter.format(12, decimalPlaces: 6), '12');
+  });
+}
diff --git a/app/test/widget_test.dart b/app/test/widget_test.dart
new file mode 100644
index 00000000..ed5574d3
--- /dev/null
+++ b/app/test/widget_test.dart
@@ -0,0 +1,19 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:unitflow/main.dart';
+
+void main() {
+  testWidgets(
+    'renders UnitFlow converter and computes a default result',
+    (WidgetTester tester) async {
+      await tester.pumpWidget(const UnitFlowApp());
+      await tester.pumpAndSettle();
+
+      expect(find.text('UnitFlow'), findsOneWidget);
+      expect(find.text('Converter'), findsOneWidget);
+      expect(find.text('Convert with confidence.'), findsOneWidget);
+      expect(find.byType(TextField), findsOneWidget);
+      expect(find.textContaining('km'), findsWidgets);
+    },
+  );
+}
diff --git a/tool/bootstrap_platforms.ps1 b/tool/bootstrap_platforms.ps1
new file mode 100644
index 00000000..ced52ea0
--- /dev/null
+++ b/tool/bootstrap_platforms.ps1
@@ -0,0 +1,13 @@
+$ErrorActionPreference = "Stop"
+
+$RootDir = Split-Path -Parent $PSScriptRoot
+Set-Location (Join-Path $RootDir "app")
+
+flutter create . `
+  --project-name unitflow `
+  --org com.sanskarin `
+  --platforms android,ios,web,windows,linux,macos
+
+flutter pub get
+
+Write-Host "UnitFlow Flutter platform folders are ready."
diff --git a/tool/bootstrap_platforms.sh b/tool/bootstrap_platforms.sh
new file mode 100644
index 00000000..fc2217ce
--- /dev/null
+++ b/tool/bootstrap_platforms.sh
@@ -0,0 +1,14 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+ROOT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+cd "$ROOT_DIR/app"
+
+flutter create . \
+  --project-name unitflow \
+  --org com.sanskarin \
+  --platforms android,ios,web,windows,linux,macos
+
+flutter pub get
+
+echo "UnitFlow Flutter platform folders are ready."