The aiming system with the guns seems a little off to me. If you click a floor tile the bullet visually passes through the tile. However, the bullet physically passes through the square below it. If bullet shadows were enabled, the bullet's shadow would show you what tile the bullet is actually passing through, thus assisting with aiming.

Another related issue is what part of the monster to click to hit it. As it stands now, you have to click a monsters head/top of box to shoot it with a gun. An option that would be useful to me would be an "floor aiming" option. So you'd click on the monsters foot/shadow to aim at it. (the bullets shadow should hit the mouse cursor, not the bullet its self)