blackout duration now adds up

actionBlocks_server/src/ActionBlocks.Game/Items/Items.cs

@@ -46,6 +46,7 @@ public sealed class InvisibilityItem : IItem
     public string Id => "blind";
     public string DisplayName => "Blackout";
 
+    // Stacks: a second Blackout adds its full duration to whatever is left.
     public void Apply(ItemContext context) =>
-        context.Target.InvisibleUntil = Math.Max(context.Target.InvisibleUntil, context.Now + DurationSeconds);
+        context.Target.InvisibleUntil = Math.Max(context.Target.InvisibleUntil, context.Now) + DurationSeconds;
 }

actionBlocks_server/tests/ActionBlocks.Game.Tests/ItemAndMatchTests.cs

@@ -90,6 +90,36 @@ public class ItemTests
         Assert.False(target.IsInvisible);
     }
 
+    [Fact]
+    public void Blackout_durations_stack()
+    {
+        var target = CreatePlayer("b");
+        target.Start();
+
+        new InvisibilityItem().Apply(Context(target, target, now: 10));
+        new InvisibilityItem().Apply(Context(target, target, now: 12));
+
+        target.Update(0.01, 17.9);
+        Assert.True(target.IsInvisible);
+        target.Update(0.01, 18.1);
+        Assert.False(target.IsInvisible);
+    }
+
+    [Fact]
+    public void Blackout_after_expiry_starts_fresh()
+    {
+        var target = CreatePlayer("b");
+        target.Start();
+
+        new InvisibilityItem().Apply(Context(target, target, now: 10));
+        new InvisibilityItem().Apply(Context(target, target, now: 20));
+
+        target.Update(0.01, 23.9);
+        Assert.True(target.IsInvisible);
+        target.Update(0.01, 24.1);
+        Assert.False(target.IsInvisible);
+    }
+
     [Fact]
     public void Registry_contains_five_unique_items()
     {