use mousedown event instead of click for faster response

tile.js

@@ -38,7 +38,7 @@ class Tile
     {
         this.elem.addEventListener("mouseenter", c => this.on_mouseenter(c));
         this.elem.addEventListener("mouseleave", c => this.on_mouseleave(c));
-        this.elem.addEventListener("click", c => this.on_click(c));
+        this.elem.addEventListener("mousedown", c => this.on_click(c));
     }
 
     reset()