HeartKeeper

Enemy variety was neat, and having a map with collision was nice, but there were some problems:

The final weapon is much worse than all previous weapons, and should be avoided. Weapons 2 and 3 are about as good as each other; weapon 2 is more reliable but weapon 3 can be useful if an excessive number of enemies begin closing on you.  Mouse controls to open the shop is not good, but luckily since there are so few items in it you will need to open the shop only a few times per game.

The real key to winning, though, seems to be hiding in a corner immediately and just using the starting gun.  I've attached a picture:

Although I stopped at 381, I think you could probably go on forever.  It's not a perfect lock, though-- you need to occasionally shoot enemies as they slowly slide in-- but it is close enough, and as the number of enemies and coins on screen grow your bullets for some reason seem to start shooting faster and doing more damage and knockback.  The game also lags like crazy with so many objects, of course, but the timer seems to be based on system or server time, not frames, so that doesn't directly impact score. You do occassionally take damage while doing this (not from any enemies but just from the game glitching out and slowly lowering your health), but changing the angle with which you are firing briefly seems to stop that, and your health either regenerates slowly even without the little red heart piece pickups or something, because the light will grow back up and you will eventually be at full health again.  The required input is why I stopped at 381, otherwise I woulda just left it running to see if it could last a couple hours or something.