This is great!
On intuitiveness: a tip said that weapons can "evolve" or whatever at level 7. But that doesn't really explain anything. I know that VS has weapon merging when you max them, but the mechanic isn't really common enough to just assume that it's the same deal here.
Maybe the tip explained that as well, but i skipped it, thinking "i'll just give it a try first", and can't find it now. This is something that's 100% going to happen!
Finally, all the coins get auto-picked-up sometimes, and i have no idea what causes that. Can't really strategize around it if i don't know.
Other than that, love the game so far. Are you planning to make a downloadable/offline version?