diff --git a/src/Domain/BasicStrategy.php b/src/Domain/BasicStrategy.php
index 6f6658e..7d0f2e9 100644
--- a/src/Domain/BasicStrategy.php
+++ b/src/Domain/BasicStrategy.php
@@ -9,11 +9,28 @@ public function decide(Hand $hand, Card $dealerCard): Decision
         $value = $hand->value();
         $dealerValue = $dealerCard->numericValue();
 
-        if ($hand->isSoft() && $value === 18 && $dealerValue >= 3 && $dealerValue <= 6) {
+        if ($hand->isSoft() && $value === 18) {
+            if ($dealerValue >= 3 && $dealerValue <= 6) {
+                return Decision::Double;
+            }
+            if ($dealerValue === 2 || $dealerValue === 7 || $dealerValue === 8) {
+                return Decision::Stand;
+            }
+            return Decision::Hit;
+        }
+
+        if ($hand->isSoft() && $value === 17) {
+            if ($dealerValue >= 3 && $dealerValue <= 6) {
+                return Decision::Double;
+            }
+            return Decision::Hit;
+        }
+
+        if ($hand->isSoft() && $value >= 15 && $value <= 16 && $dealerValue >= 4 && $dealerValue <= 6) {
             return Decision::Double;
         }
 
-        if ($hand->isSoft() && $value === 17 && $dealerValue >= 3 && $dealerValue <= 6) {
+        if ($hand->isSoft() && $value >= 13 && $value <= 14 && $dealerValue >= 5 && $dealerValue <= 6) {
             return Decision::Double;
         }
 
@@ -21,11 +38,19 @@ public function decide(Hand $hand, Card $dealerCard): Decision
             return Decision::Stand;
         }
 
-        if ($value >= 13 && $value <= 16 && $dealerValue >= 2 && $dealerValue <= 6) {
+        if (!$hand->isSoft() && $value === 16 && ($dealerValue === 9 || $dealerValue === 10 || $dealerValue === 11)) {
+            return Decision::Surrender;
+        }
+
+        if (!$hand->isSoft() && $value === 15 && $dealerValue === 10) {
+            return Decision::Surrender;
+        }
+
+        if (!$hand->isSoft() && $value >= 13 && $value <= 16 && $dealerValue >= 2 && $dealerValue <= 6) {
             return Decision::Stand;
         }
 
-        if ($value === 12 && $dealerValue >= 4 && $dealerValue <= 6) {
+        if (!$hand->isSoft() && $value === 12 && $dealerValue >= 4 && $dealerValue <= 6) {
             return Decision::Stand;
         }
 
@@ -43,4 +68,4 @@ public function decide(Hand $hand, Card $dealerCard): Decision
 
         return Decision::Hit;
     }
-}
\ No newline at end of file
+}
diff --git a/src/Domain/Decision.php b/src/Domain/Decision.php
index 048bb31..8983bba 100644
--- a/src/Domain/Decision.php
+++ b/src/Domain/Decision.php
@@ -8,4 +8,5 @@ enum Decision
     case Stand;
     case Double;
     case Split;
+    case Surrender;
 }
\ No newline at end of file
diff --git a/tests/Domain/BasicStrategyTest.php b/tests/Domain/BasicStrategyTest.php
index d908571..eeaa732 100644
--- a/tests/Domain/BasicStrategyTest.php
+++ b/tests/Domain/BasicStrategyTest.php
@@ -10,7 +10,7 @@
 
 final class BasicStrategyTest extends TestCase
 {
-    public function testHard16AgainstDealerTenShouldHit(): void
+    public function testHard16AgainstDealerTenShouldSurrender(): void
     {
         $strategy = new BasicStrategy();
 
@@ -20,7 +20,7 @@ public function testHard16AgainstDealerTenShouldHit(): void
 
         $dealerCard = new Card('10', 'Diamonds');
 
-        $this->assertSame(Decision::Hit, $strategy->decide($hand, $dealerCard));
+        $this->assertSame(Decision::Surrender, $strategy->decide($hand, $dealerCard));
     }
 
     public function testHard17ShouldStand(): void
@@ -35,6 +35,7 @@ public function testHard17ShouldStand(): void
 
         $this->assertSame(Decision::Stand, $strategy->decide($hand, $dealerCard));
     }
+
     public function testHard12AgainstDealer4ShouldStand(): void
     {
         $strategy = new BasicStrategy();
@@ -151,4 +152,238 @@ public function testSoft19ShouldAlwaysStand(): void
 
         $this->assertSame(Decision::Stand, $strategy->decide($hand, $dealerCard));
     }
+
+    public function testSoft18AgainstDealer9ShouldHit(): void
+    {
+        $strategy = new BasicStrategy();
+
+        $hand = new Hand();
+        $hand->addCard(new Card('Ace', 'Hearts'));
+        $hand->addCard(new Card('7', 'Spades'));
+
+        $dealerCard = new Card('9', 'Diamonds');
+
+        $this->assertSame(Decision::Hit, $strategy->decide($hand, $dealerCard));
+    }
+
+    public function testSoft15AgainstDealer4ShouldDouble(): void
+    {
+        $strategy = new BasicStrategy();
+
+        $hand = new Hand();
+        $hand->addCard(new Card('Ace', 'Hearts'));
+        $hand->addCard(new Card('4', 'Spades'));
+
+        $dealerCard = new Card('4', 'Diamonds');
+
+        $this->assertSame(Decision::Double, $strategy->decide($hand, $dealerCard));
+    }
+
+    public function testSoft13AgainstDealer5ShouldDouble(): void
+    {
+        $strategy = new BasicStrategy();
+
+        $hand = new Hand();
+        $hand->addCard(new Card('Ace', 'Hearts'));
+        $hand->addCard(new Card('2', 'Spades'));
+
+        $dealerCard = new Card('5', 'Diamonds');
+
+        $this->assertSame(Decision::Double, $strategy->decide($hand, $dealerCard));
+    }
+
+    public function testHard12AgainstDealer2ShouldHit(): void
+    {
+        $strategy = new BasicStrategy();
+
+        $hand = new Hand();
+        $hand->addCard(new Card('7', 'Hearts'));
+        $hand->addCard(new Card('5', 'Spades'));
+
+        $dealerCard = new Card('2', 'Diamonds');
+
+        $this->assertSame(Decision::Hit, $strategy->decide($hand, $dealerCard));
+    }
+
+    public function testHard12AgainstDealer3ShouldHit(): void
+    {
+        $strategy = new BasicStrategy();
+
+        $hand = new Hand();
+        $hand->addCard(new Card('7', 'Hearts'));
+        $hand->addCard(new Card('5', 'Spades'));
+
+        $dealerCard = new Card('3', 'Diamonds');
+
+        $this->assertSame(Decision::Hit, $strategy->decide($hand, $dealerCard));
+    }
+
+    public function testSoft17AgainstDealer7ShouldHit(): void
+    {
+        $strategy = new BasicStrategy();
+
+        $hand = new Hand();
+        $hand->addCard(new Card('Ace', 'Hearts'));
+        $hand->addCard(new Card('6', 'Spades'));
+
+        $dealerCard = new Card('7', 'Diamonds');
+
+        $this->assertSame(Decision::Hit, $strategy->decide($hand, $dealerCard));
+    }
+
+    public function testSoft13AgainstDealer7ShouldHit(): void
+    {
+        $strategy = new BasicStrategy();
+
+        $hand = new Hand();
+        $hand->addCard(new Card('Ace', 'Hearts'));
+        $hand->addCard(new Card('2', 'Spades'));
+
+        $dealerCard = new Card('7', 'Diamonds');
+
+        $this->assertSame(Decision::Hit, $strategy->decide($hand, $dealerCard));
+    }
+
+    public function testSoft13AgainstDealer4ShouldHit(): void
+    {
+        $strategy = new BasicStrategy();
+
+        $hand = new Hand();
+        $hand->addCard(new Card('Ace', 'Hearts'));
+        $hand->addCard(new Card('2', 'Spades'));
+
+        $dealerCard = new Card('4', 'Diamonds');
+
+        $this->assertSame(Decision::Hit, $strategy->decide($hand, $dealerCard));
+    }
+
+    public function testSoft16AgainstDealer7ShouldHit(): void
+    {
+        $strategy = new BasicStrategy();
+
+        $hand = new Hand();
+        $hand->addCard(new Card('Ace', 'Hearts'));
+        $hand->addCard(new Card('5', 'Spades'));
+
+        $dealerCard = new Card('7', 'Diamonds');
+
+        $this->assertSame(Decision::Hit, $strategy->decide($hand, $dealerCard));
+    }
+
+    public function testHard11AgainstDealerAceShouldHit(): void
+    {
+        $strategy = new BasicStrategy();
+
+        $hand = new Hand();
+        $hand->addCard(new Card('7', 'Hearts'));
+        $hand->addCard(new Card('4', 'Spades'));
+
+        $dealerCard = new Card('Ace', 'Diamonds');
+
+        $this->assertSame(Decision::Hit, $strategy->decide($hand, $dealerCard));
+    }
+
+    public function testHard10AgainstDealerAceShouldHit(): void
+    {
+        $strategy = new BasicStrategy();
+
+        $hand = new Hand();
+        $hand->addCard(new Card('6', 'Hearts'));
+        $hand->addCard(new Card('4', 'Spades'));
+
+        $dealerCard = new Card('Ace', 'Diamonds');
+
+        $this->assertSame(Decision::Hit, $strategy->decide($hand, $dealerCard));
+    }
+
+    public function testHard16AgainstDealer9ShouldSurrender(): void
+    {
+        $strategy = new BasicStrategy();
+
+        $hand = new Hand();
+        $hand->addCard(new Card('9', 'Hearts'));
+        $hand->addCard(new Card('7', 'Spades'));
+
+        $dealerCard = new Card('9', 'Diamonds');
+
+        $this->assertSame(Decision::Surrender, $strategy->decide($hand, $dealerCard));
+    }
+
+    public function testHard15AgainstDealerTenShouldSurrender(): void
+    {
+        $strategy = new BasicStrategy();
+
+        $hand = new Hand();
+        $hand->addCard(new Card('9', 'Hearts'));
+        $hand->addCard(new Card('6', 'Spades'));
+
+        $dealerCard = new Card('10', 'Diamonds');
+
+        $this->assertSame(Decision::Surrender, $strategy->decide($hand, $dealerCard));
+    }
+
+    public function testHard16AgainstDealerAceShouldSurrender(): void
+    {
+        $strategy = new BasicStrategy();
+
+        $hand = new Hand();
+        $hand->addCard(new Card('9', 'Hearts'));
+        $hand->addCard(new Card('7', 'Spades'));
+
+        $dealerCard = new Card('Ace', 'Diamonds');
+
+        $this->assertSame(Decision::Surrender, $strategy->decide($hand, $dealerCard));
+    }
+
+    public function testHard8ShouldAlwaysHit(): void
+    {
+        $strategy = new BasicStrategy();
+
+        $hand = new Hand();
+        $hand->addCard(new Card('4', 'Hearts'));
+        $hand->addCard(new Card('4', 'Spades'));
+
+        $dealerCard = new Card('6', 'Diamonds');
+
+        $this->assertSame(Decision::Hit, $strategy->decide($hand, $dealerCard));
+    }
+
+    public function testHard9AgainstDealer2ShouldHit(): void
+    {
+        $strategy = new BasicStrategy();
+
+        $hand = new Hand();
+        $hand->addCard(new Card('5', 'Hearts'));
+        $hand->addCard(new Card('4', 'Spades'));
+
+        $dealerCard = new Card('2', 'Diamonds');
+
+        $this->assertSame(Decision::Hit, $strategy->decide($hand, $dealerCard));
+    }
+
+    public function testHard9AgainstDealer7ShouldHit(): void
+    {
+        $strategy = new BasicStrategy();
+
+        $hand = new Hand();
+        $hand->addCard(new Card('5', 'Hearts'));
+        $hand->addCard(new Card('4', 'Spades'));
+
+        $dealerCard = new Card('7', 'Diamonds');
+
+        $this->assertSame(Decision::Hit, $strategy->decide($hand, $dealerCard));
+    }
+
+    public function testHard16AgainstDealer7ShouldHit(): void
+    {
+        $strategy = new BasicStrategy();
+
+        $hand = new Hand();
+        $hand->addCard(new Card('9', 'Hearts'));
+        $hand->addCard(new Card('7', 'Spades'));
+
+        $dealerCard = new Card('7', 'Diamonds');
+
+        $this->assertSame(Decision::Hit, $strategy->decide($hand, $dealerCard));
+    }
 }
\ No newline at end of file