On the whole, a fun idea and neat execution. Some weapons feel worse than the base pistol. A few things I found during play: holding enter after selecting ammo lets you continue to buy without wasting ammo of your equipped weapon. If you exit to menu and come back, bought upgrades revert to original price until you buy one of them and bought weapons show up as unbought, although you can still equip them. Finally, if you have a sword equipped and drag out of the games focus, the weapon doesn't do the attack.