feat: Add F3 debug mode with collision boxes and FPS display

js/entities/entity.js

@@ -62,6 +62,24 @@ class Entity {
             );
         }
         
+        // Draw collision box in debug mode
+        if (debugMode) {
+            ctx.strokeStyle = '#00ff00';
+            ctx.lineWidth = 1;
+            ctx.strokeRect(
+                -this.width/2 * PIXEL_SIZE, 
+                -this.height/2 * PIXEL_SIZE, 
+                this.width * PIXEL_SIZE, 
+                this.height * PIXEL_SIZE
+            );
+            
+            // Draw a dot at the entity's center
+            ctx.fillStyle = '#ffff00';
+            ctx.beginPath();
+            ctx.arc(0, 0, 2, 0, Math.PI * 2);
+            ctx.fill();
+        }
+        
         ctx.restore();
     }