That's how it looks to me: https://gyazo.com/bb3d1c30bfcdcc64927b5f5833aa29f0 For some reason, the edges changes to an object which moves there, but that always happens to me, not only here at your scenario...

Oh I forgot, the lag on my laptop isn't that bad. It is playable at least. Can't test on other one, but I didn't change anything to reduce it.

Just some ideas: - in my opinion it would be better to use 'mousePressed' instead of 'mouseClicked' - maybe instead of just clicking on a bomb, shoot on them with projectiles to destroy them (for that, the bombs should move slower) - the snowmen shouldn't be transparent ;) - bombs that doesn't hit anything should have some effect, too. Maybe decrease score. Or you lose the game when only 5 snowmen/igloos are left, but every bomb is ejected over a snowman/igloo