Pretty basic game, I liked the upgrading, it seemed like there was JUST enough money going through the game in one go to get everything and have about 1000$ left over, so that's all good, the only problem I would have had would be to maybe fill that final weapon slot[blank space in the shop] with like a chainsaw, max damage and speed of attack, but ridiculously low range. Or perhaps a character specific weapon.
Overall, good game!