I'm giving this a 3.5 for a few reasons.
1. Weapon upgrades are random as all hell and don't seem to compete with the gems/bateria/whatever it is they are.
2. I don't know if I can even beat this game, which is bad. You either should disclose that right away or make it level based and have and endless mode, don't just make it endless and not tell anyone.
3. Upgrades, by making it level based, each time you kill the wave, allow for a chance to purchase them, can add bombs etc. Ways to make it less than just the same thing but oh hey look your shot gun is now a lazer and you still can't keep up with the massive swarm.
4. No real sense of purpose behind it, the waves come and go and it's just the same thing maybe a new color or once in awhile you get a new monster, but yeah.
5. No wave counter, an idea of how many i have left to wipe out would be nice and handy as i can concentrate on the smaller vs bigger if i had an idea of number rather than cluster fuck.
Over all the music was good, gameplay as it stands is solid. It just needs to be tweaked some to make it more lively and more of a sense of getting somewhere instead of hey just keep doing this till you...die. Yeah.