Add and improve domain (WIP)

composeApp/src/commonMain/kotlin/domain/Game.kt

@@ -0,0 +1,21 @@
+package domain
+
+class Game(
+    val categories: List<ItemCategory>,
+    val grid: Grid,
+    val horizontalRules: List<HorizontalRule>,
+    val verticalRules: List<VerticalRule>
+) {
+    fun areCategoriesValid(): Boolean = categories.mapIndexed { index, category ->
+        category.any { item ->
+            categories.filterIndexed { i, _ -> i > index }.any { it.contains(item) }
+        }
+    }.none { it }
+
+    fun areRulesViolated(): Boolean = horizontalRules
+        .map { it.isRuleViolated(grid) }
+        .reduce { a, b -> a || b }
+            || verticalRules
+        .map { it.isRuleViolated(grid) }
+        .reduce { a, b -> a || b }
+}