Add attribute system with core stats and gameplay components

GameCore/Attributes/Attribute.cs

@@ -0,0 +1,31 @@
+namespace GameCore.Attributes;
+
+/// <summary>
+///     Defines all possible stats an entity can have.
+/// </summary>
+public enum Attribute
+{
+    // Core Stats
+    Health,
+    MaxHealth,
+    Armor,
+    MoveSpeed,
+    Acceleration,
+    Friction,
+    JumpHeight,
+
+    // Combat Stats
+    Damage,
+    AttackSpeed,
+    AttackRange,
+    MeleeDamage, // Multiplier
+    RangedDamage, // Multiplier
+
+    // Progression
+    Level,
+    Experience,
+    ExperienceToNextLevel,
+
+    // Misc
+    Luck
+}

GameCore/Attributes/AttributeComponent.cs

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+using GameCore.ECS.Interfaces;
+
+namespace GameCore.Attributes;
+
+/// <summary>
+///     A component that stores all gameplay-relevant stats for an entity.
+///     This design is adapted directly from the excellent CharacterAttributes class
+///     in the 'broberry' project. It's a flexible, data-driven way to manage stats.
+/// </summary>
+public class AttributeComponent : IComponent
+{
+    public readonly Dictionary<Attribute, float> BaseValues = new();
+    public readonly Dictionary<Attribute, float> CurrentValues = new();
+
+    public event Action<Attribute, float>? OnAttributeChanged;
+
+    public void SetBaseValue(Attribute attr, float value)
+    {
+        BaseValues[attr] = value;
+        SetCurrentValue(attr, value);
+    }
+
+    public float GetValue(Attribute attr)
+    {
+        return CurrentValues.GetValueOrDefault(attr, 0f);
+    }
+
+    public void ModifyValue(Attribute attr, float delta)
+    {
+        var newValue = GetValue(attr) + delta;
+        SetCurrentValue(attr, newValue);
+    }
+
+    public void SetCurrentValue(Attribute attr, float value, bool force = false)
+    {
+        if (CurrentValues.TryGetValue(attr, out var oldValue) && !(System.Math.Abs(oldValue - value) > 0.001f) &&
+            !force) return;
+
+        CurrentValues[attr] = value;
+        OnAttributeChanged?.Invoke(attr, value);
+    }
+}

GameCore/Attributes/AttributeSystem.cs

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+using GameCore.ECS;
+using GameCore.ECS.Interfaces;
+
+namespace GameCore.Attributes;
+
+public class AttributeSystem : ISystem
+{
+    public void Update(World world, float deltaTime)
+    {
+        var entities = world.GetEntitiesWith<AttributeComponent>();
+
+        foreach (var entity in entities)
+        {
+            var attributes = world.GetComponent<AttributeComponent>(entity);
+            if (attributes == null) continue;
+
+            var maxHealth = attributes.GetValue(Attribute.MaxHealth);
+            var currentHealth = attributes.GetValue(Attribute.Health);
+
+            if (currentHealth > maxHealth) attributes.SetCurrentValue(Attribute.Health, maxHealth);
+        }
+    }
+}