Drag one of 6 towers on the upper side down onto one of the tiles to place it. Then press the arrow to start. Enemies(which are the dots coming from the left) damage you when they go to the right. But the towers can destroy them before that happens. If you like this, please consider loving and/or favoriting it.
Try the original project if you want a challenge because this is a sandbox. Beware of the man who speaks in hands