diff --git a/doc/prices.png b/doc/prices.png
new file mode 100644
index 0000000..0b82c0f
Binary files /dev/null and b/doc/prices.png differ
diff --git a/phpunit.xml b/phpunit.xml
index 01e21e2..1ea1df0 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -8,6 +8,7 @@
          beStrictAboutOutputDuringTests="true"
          beStrictAboutTodoAnnotatedTests="true"
          verbose="true"
+         testdox="true"
          colors="true">
     <testsuites>
         <testsuite name="default">
diff --git a/src/Game.php b/src/Game.php
new file mode 100644
index 0000000..d57e55b
--- /dev/null
+++ b/src/Game.php
@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ClansOfCaledonia;
+
+use ClansOfCaledonia\Good\Grain;
+use ClansOfCaledonia\Good\Milk;
+use ClansOfCaledonia\Good\Wool;
+
+final class Game
+{
+    const GOODS = [ // TODO: Improve this
+        'Milk',
+        'Wool',
+        'Grain',
+    ];
+
+    public static function main(Pound $money): void
+    {
+        $priceBuilder = new PriceListBuilder();
+
+        $market = (new Market)
+            ->withPriceList(Milk::name(), $priceBuilder->milkPrices())
+            ->withPriceList(Wool::name(), $priceBuilder->woolPrices())
+            ->withPriceList(Grain::name(), $priceBuilder->grainPrices());
+
+        $player = new Player($money, $market);
+        while (true) {
+            echo sprintf('You have %i pounds', $player->money());
+            $goodName = readline(sprintf('What do you want to buy now? (%s)', implode(',', self::GOODS)));
+            $amount = (int)readline('How many pounds?');
+            $player->buy(new Unit($amount), Good::byName($goodName));
+            static::printMarket($market);
+            sleep(1);
+        }
+    }
+
+    private static function printMarket(Market $market)
+    {
+        foreach($market->allPriceList() as $goodName => $priceList){
+            echo $goodName.PHP_EOL;
+            foreach($priceList as $price) {
+                // display the table
+            }
+            echo PHP_EOL;
+        }
+    }
+}
diff --git a/src/Good.php b/src/Good.php
index 2e540c6..431d96b 100644
--- a/src/Good.php
+++ b/src/Good.php
@@ -1,11 +1,45 @@
 <?php declare(strict_types=1);
+
 namespace ClansOfCaledonia;
 
+use ClansOfCaledonia\Good\Grain;
+use ClansOfCaledonia\Good\Milk;
+use ClansOfCaledonia\Good\Wool;
+
 abstract class Good
 {
+    public static function name(): string
+    {
+        return static::class;
+    }
+
     public static function milk(): self
     {
-        return new Milk;
+        return new Milk();
+    }
+
+    public static function wool(): self
+    {
+        return new Wool();
+    }
+
+    public static function grain(): self
+    {
+        return new Grain();
+    }
+
+    public static function byName(string $goodName)
+    {
+        switch ($goodName){
+            case Milk::name():
+                return self::milk();
+            case Wool::name():
+                return self::wool();
+            case Grain::name():
+                return self::grain();
+        }
+
+        throw new \Exception('Good Unknown');
     }
 
     public function isMilk(): bool
diff --git a/src/Good/Grain.php b/src/Good/Grain.php
new file mode 100644
index 0000000..9cd0670
--- /dev/null
+++ b/src/Good/Grain.php
@@ -0,0 +1,9 @@
+<?php declare(strict_types=1);
+
+namespace ClansOfCaledonia\Good;
+
+use ClansOfCaledonia\Good;
+
+final class Grain extends Good
+{
+}
diff --git a/src/Good/Milk.php b/src/Good/Milk.php
new file mode 100644
index 0000000..6e396bd
--- /dev/null
+++ b/src/Good/Milk.php
@@ -0,0 +1,18 @@
+<?php declare(strict_types=1);
+
+namespace ClansOfCaledonia\Good;
+
+use ClansOfCaledonia\Good;
+
+final class Milk extends Good
+{
+    public static function name(): string
+    {
+        return 'Milk';
+    }
+
+    public function isMilk(): bool
+    {
+        return true;
+    }
+}
diff --git a/src/Good/Wool.php b/src/Good/Wool.php
new file mode 100644
index 0000000..f195d87
--- /dev/null
+++ b/src/Good/Wool.php
@@ -0,0 +1,9 @@
+<?php declare(strict_types=1);
+
+namespace ClansOfCaledonia\Good;
+
+use ClansOfCaledonia\Good;
+
+final class Wool extends Good
+{
+}
diff --git a/src/Market.php b/src/Market.php
index cfe5ae3..4a5626f 100644
--- a/src/Market.php
+++ b/src/Market.php
@@ -1,18 +1,43 @@
 <?php declare(strict_types=1);
+
 namespace ClansOfCaledonia;
 
 final class Market
 {
-    public function priceFor(Good $milk): Pound
+    /** @var array<string,PriceList> */
+    private $prices;
+
+    public function __construct()
     {
-        return new Pound(5);
+        $this->prices = [];
+    }
+
+    public function withPriceList(string $goodName, PriceList $priceList): self
+    {
+        $this->prices[$goodName] = $priceList;
+
+        return $this;
+    }
+
+    public function priceFor(Good $good): Pound
+    {
+        return $this->prices[$good->name()]->current();
     }
 
     public function sellTo(Offer $offer): Pound
     {
-        return new Pound(
-            $offer->amount()->amount() *
-            $this->priceFor($offer->good())->amount()
-        );
+        $good = $offer->good();
+        $unit = $offer->amount();
+        $payment = $this->priceFor($good)->multiply($unit->amount());
+        $this->adjustPrice($good, $unit);
+
+        return $payment;
+    }
+
+    private function adjustPrice(Good $good, Unit $unit)
+    {
+        /** @var PriceList $priceList */
+        $priceList = $this->prices[$good->name()];
+        $priceList->moveTo($unit);
     }
 }
diff --git a/src/Milk.php b/src/Milk.php
deleted file mode 100644
index 8689abe..0000000
--- a/src/Milk.php
+++ /dev/null
@@ -1,10 +0,0 @@
-<?php declare(strict_types=1);
-namespace ClansOfCaledonia;
-
-final class Milk extends Good
-{
-    public function isMilk(): bool
-    {
-        return true;
-    }
-}
diff --git a/src/Player.php b/src/Player.php
new file mode 100644
index 0000000..4102a8a
--- /dev/null
+++ b/src/Player.php
@@ -0,0 +1,29 @@
+<?php declare(strict_types=1);
+
+namespace ClansOfCaledonia;
+
+final class Player
+{
+    /** @var Pound */
+    private $money;
+
+    /** @var Market */
+    private $market;
+
+    public function __construct(Pound $money, Market $market)
+    {
+        $this->money = $money;
+        $this->market = $market;
+    }
+
+    public function buy(Unit $unit, Good $good): void
+    {
+        $payment = $this->market->sellTo(new Offer($unit, $good));
+        $this->money = $this->money->minus($payment->amount());
+    }
+
+    public function money(): Pound
+    {
+        return $this->money;
+    }
+}
diff --git a/src/Pound.php b/src/Pound.php
index 1be124e..069a23a 100644
--- a/src/Pound.php
+++ b/src/Pound.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace ClansOfCaledonia;
 
 final class Pound
@@ -17,4 +18,14 @@ public function amount(): int
     {
         return $this->amount;
     }
+
+    public function multiply(int $factor): Pound
+    {
+        return new Pound($this->amount * $factor);
+    }
+
+    public function minus(int $number): Pound
+    {
+        return new Pound($this->amount - $number);
+    }
 }
diff --git a/src/PriceList.php b/src/PriceList.php
index 8a6a231..2368de0 100644
--- a/src/PriceList.php
+++ b/src/PriceList.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace ClansOfCaledonia;
 
 final class PriceList
@@ -11,18 +12,20 @@ final class PriceList
     /**
      * @var int
      */
-    private $position = 3;
+    private $position;
 
-    public static function fromList(Pound ...$pounds): self
+    public static function fromList(int $initPosition, Pound ...$pounds): self
     {
-        return new self($pounds);
+        return new self($initPosition, $pounds);
     }
 
     /**
+     * @param int $initPosition
      * @param Pound[] $prices
      */
-    private function __construct(array $prices)
+    private function __construct(int $initPosition, array $prices)
     {
+        $this->position = $initPosition;
         $this->prices = $prices;
     }
 
@@ -30,4 +33,9 @@ public function current(): Pound
     {
         return $this->prices[$this->position];
     }
+
+    public function moveTo(Unit $unit): void
+    {
+        $this->position += $unit->amount();
+    }
 }
diff --git a/src/PriceListBuilder.php b/src/PriceListBuilder.php
index bc0da06..8c5995b 100644
--- a/src/PriceListBuilder.php
+++ b/src/PriceListBuilder.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace ClansOfCaledonia;
 
 final class PriceListBuilder
@@ -6,6 +7,7 @@ final class PriceListBuilder
     public function milkPrices(): PriceList
     {
         return PriceList::fromList(
+            $initPosition = 3,
             new Pound(3),
             new Pound(4),
             new Pound(5),
@@ -18,4 +20,38 @@ public function milkPrices(): PriceList
             new Pound(8)
         );
     }
+
+    public function woolPrices(): PriceList
+    {
+        return PriceList::fromList(
+            $initPosition = 3,
+            new Pound(3),
+            new Pound(3),
+            new Pound(4),
+            new Pound(4),
+            new Pound(5),
+            new Pound(5),
+            new Pound(6),
+            new Pound(6),
+            new Pound(7),
+            new Pound(8)
+        );
+    }
+
+    public function grainPrices(): PriceList
+    {
+        return PriceList::fromList(
+            $initPosition = 3,
+            new Pound(3),
+            new Pound(3),
+            new Pound(4),
+            new Pound(5),
+            new Pound(6),
+            new Pound(6),
+            new Pound(7),
+            new Pound(7),
+            new Pound(8),
+            new Pound(8)
+        );
+    }
 }
diff --git a/src/autoload.php b/src/autoload.php
index 1078cb5..7a65add 100644
--- a/src/autoload.php
+++ b/src/autoload.php
@@ -9,10 +9,13 @@ function($class) {
             $classes = array(
                 'clansofcaledonia\\exception' => '/Exception.php',
                 'clansofcaledonia\\good' => '/Good.php',
+                'clansofcaledonia\\good\\grain' => '/Good/Grain.php',
+                'clansofcaledonia\\good\\milk' => '/Good/Milk.php',
+                'clansofcaledonia\\good\\wool' => '/Good/Wool.php',
                 'clansofcaledonia\\market' => '/Market.php',
-                'clansofcaledonia\\milk' => '/Milk.php',
                 'clansofcaledonia\\offer' => '/Offer.php',
                 'clansofcaledonia\\outofrangeexception' => '/OutOfRangeException.php',
+                'clansofcaledonia\\player' => '/Player.php',
                 'clansofcaledonia\\pound' => '/Pound.php',
                 'clansofcaledonia\\pricelist' => '/PriceList.php',
                 'clansofcaledonia\\pricelistbuilder' => '/PriceListBuilder.php',
diff --git a/tests/GoodTest.php b/tests/Good/GoodTest.php
similarity index 61%
rename from tests/GoodTest.php
rename to tests/Good/GoodTest.php
index f44ff47..cd19b21 100644
--- a/tests/GoodTest.php
+++ b/tests/Good/GoodTest.php
@@ -1,6 +1,8 @@
 <?php declare(strict_types=1);
-namespace ClansOfCaledonia;
 
+namespace ClansOfCaledonia\Good;
+
+use ClansOfCaledonia\Good;
 use PHPUnit\Framework\TestCase;
 
 /**
@@ -15,4 +17,11 @@ public function testCanBeMilk(): void
 
         $this->assertTrue($milk->isMilk());
     }
+
+    public function testCanNotBeMilk(): void
+    {
+        $grain = Good::grain();
+
+        $this->assertFalse($grain->isMilk());
+    }
 }
diff --git a/tests/MarketTest.php b/tests/MarketTest.php
index d01128e..83be875 100644
--- a/tests/MarketTest.php
+++ b/tests/MarketTest.php
@@ -1,39 +1,56 @@
 <?php declare(strict_types=1);
+
 namespace ClansOfCaledonia;
 
+use ClansOfCaledonia\Good\Milk;
 use PHPUnit\Framework\TestCase;
 
 /**
  * @covers \ClansOfCaledonia\Market
  *
- * @uses \ClansOfCaledonia\Pound
- * @uses \ClansOfCaledonia\Good
- * @uses \ClansOfCaledonia\Offer
- * @uses \ClansOfCaledonia\Unit
+ * @uses   \ClansOfCaledonia\Pound
+ * @uses   \ClansOfCaledonia\Good
+ * @uses   \ClansOfCaledonia\Offer
+ * @uses   \ClansOfCaledonia\Unit
  */
 final class MarketTest extends TestCase
 {
-    public function testMilkCosts5PoundsInitially(): void
+    /** @var Market */
+    private $market;
+
+    public function setUp(): void
     {
-        $market = new Market;
+        $this->market = (new Market)
+            ->withPriceList(
+                Milk::name(),
+                PriceList::fromList(
+                    $initPosition = 0,
+                    new Pound(10),
+                    new Pound(20),
+                    new Pound(30),
+                    new Pound(40),
+                    new Pound(50)
+                )
+            );
+    }
 
-        $this->assertEquals(new Pound(5), $market->priceFor(Good::milk()));
+    public function testInitialPoundsFromInitPosition(): void
+    {
+        $this->assertEquals(new Pound(10), $this->market->priceFor(Good::milk()));
     }
 
     public function testMilkCanBeSoldToTheMarket(): Market
     {
-        $market = new Market;
-
-        $payment = $market->sellTo(
+        $payment = $this->market->sellTo(
             new Offer(
-                new Unit(2),
+                new Unit(3),
                 Good::milk()
             )
         );
 
-        $this->assertEquals(new Pound(10), $payment);
+        $this->assertEquals(new Pound(30), $payment);
 
-        return $market;
+        return $this->market;
     }
 
     /**
@@ -41,6 +58,6 @@ public function testMilkCanBeSoldToTheMarket(): Market
      */
     public function testSellingMilkToTheMarketReducesMilkPrice(Market $market): void
     {
-        $this->assertEquals(new Pound(4), $market->priceFor(Good::milk()));
+        $this->assertEquals(new Pound(40), $market->priceFor(Good::milk()));
     }
 }
diff --git a/tests/PlayerTest.php b/tests/PlayerTest.php
new file mode 100644
index 0000000..8e02e91
--- /dev/null
+++ b/tests/PlayerTest.php
@@ -0,0 +1,38 @@
+<?php declare(strict_types=1);
+
+namespace ClansOfCaledonia;
+
+use ClansOfCaledonia\Good\Milk;
+use PHPUnit\Framework\TestCase;
+
+/**
+ * @covers \ClansOfCaledonia\Player
+ *
+ * @uses   \ClansOfCaledonia\Market
+ */
+final class PlayerTest extends TestCase
+{
+    public function testPlayerPoundsGetReducesAfterBuyingAGood(): void
+    {
+        $good = Good::milk();
+        $market = (new Market)
+            ->withPriceList(
+                $good::name(),
+                PriceList::fromList(
+                    $initPosition = 0,
+                    new Pound(10),
+                    new Pound(20),
+                    new Pound(30),
+                    new Pound(40),
+                    new Pound(50)
+                ));
+
+        $initPounds = new Pound(100);
+        $player = new Player($initPounds, $market);
+        $player->buy(new Unit(2), Good::milk());
+
+        $this->assertEquals(new Pound(80), $player->money());
+        $this->assertEquals(new Pound(30), $market->priceFor($good));
+    }
+
+}
diff --git a/tests/PoundTest.php b/tests/PoundTest.php
index 3d3ec6d..0b593a4 100644
--- a/tests/PoundTest.php
+++ b/tests/PoundTest.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace ClansOfCaledonia;
 
 use PHPUnit\Framework\TestCase;
@@ -16,4 +17,37 @@ public function testHasAmount(): void
 
         $this->assertSame($amount, $p->amount());
     }
+
+    /**
+     * @dataProvider multiplyFactors
+     */
+    public function testCanBeMultiplyByAFactor(int $init, int $factor, int $result): void
+    {
+        $this->assertEquals(new Pound($result), (new Pound($init))->multiply($factor));
+    }
+
+    public function multiplyFactors(): array
+    {
+        return [
+            [2, 2, 4],
+            [2, 5, 10],
+            [3, 2, 6],
+        ];
+    }
+    /**
+     * @dataProvider minusNumbers
+     */
+    public function testCanBeMinusByANumber(int $init, int $factor, int $result): void
+    {
+        $this->assertEquals(new Pound($result), (new Pound($init))->minus($factor));
+    }
+
+    public function minusNumbers(): array
+    {
+        return [
+            [2, 2, 0],
+            [2, 5, -3],
+            [3, 2, 1],
+        ];
+    }
 }
diff --git a/tests/PriceListBuilderTest.php b/tests/PriceListBuilderTest.php
index 5df7e04..27fdfd5 100644
--- a/tests/PriceListBuilderTest.php
+++ b/tests/PriceListBuilderTest.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace ClansOfCaledonia;
 
 use PHPUnit\Framework\TestCase;
@@ -6,8 +7,8 @@
 /**
  * @covers \ClansOfCaledonia\PriceListBuilder
  *
- * @uses \ClansOfCaledonia\PriceList
- * @uses \ClansOfCaledonia\Pound
+ * @uses   \ClansOfCaledonia\PriceList
+ * @uses   \ClansOfCaledonia\Pound
  */
 final class PriceListBuilderTest extends TestCase
 {
@@ -19,4 +20,22 @@ public function testCanBuildMilkPriceList(): void
 
         $this->assertEquals(new Pound(5), $milkPrices->current());
     }
+
+    public function testCanBuildWoolPriceList(): void
+    {
+        $builder = new PriceListBuilder;
+
+        $milkPrices = $builder->woolPrices();
+
+        $this->assertEquals(new Pound(4), $milkPrices->current());
+    }
+
+    public function testCanBuildGrainPriceList(): void
+    {
+        $builder = new PriceListBuilder;
+
+        $milkPrices = $builder->grainPrices();
+
+        $this->assertEquals(new Pound(5), $milkPrices->current());
+    }
 }
diff --git a/tests/PriceListTest.php b/tests/PriceListTest.php
index aba7abb..ab9278f 100644
--- a/tests/PriceListTest.php
+++ b/tests/PriceListTest.php
@@ -1,4 +1,5 @@
 <?php declare(strict_types=1);
+
 namespace ClansOfCaledonia;
 
 use PHPUnit\Framework\TestCase;
@@ -6,13 +7,14 @@
 /**
  * @covers \ClansOfCaledonia\PriceList
  *
- * @uses \ClansOfCaledonia\Pound
+ * @uses   \ClansOfCaledonia\Pound
  */
 final class PriceListTest extends TestCase
 {
     public function testHasInitialPrice(): void
     {
         $prices = PriceList::fromList(
+            $initPosition = 1,
             new Pound(1),
             new Pound(2),
             new Pound(3),
@@ -25,6 +27,6 @@ public function testHasInitialPrice(): void
             new Pound(10)
         );
 
-        $this->assertEquals(new Pound(4), $prices->current());
+        $this->assertEquals(new Pound(2), $prices->current());
     }
 }