In old PCs it gets too slow even in low quality. I'm sure you can do something to make it faster. It must be perfect in the last Core i7. My hardware is 2006 and I can play Crysis fine but this is almost unplayable.
It reminds me to Dragon Spirit for Nintendo 8-Bits. In that game you get the upgrades by killing enemies which was sad because when you die you loose everything but the good part was that those upgrades made your dragon evolve and get different kind of shots (Multiple heads = Multiple shots...)