At first I thought ...huh that game is very simple and solid but there is nothing much to it... but then I cleared the first wave and you provide the player with actually very significant upgrades. Props to you, I didn't expect that
I'm still unsure of how exactly the combo system works but I can tell that you can heal yourself with it, it provides you extra time and you loose your combo when you get hit. Not sure though why you sometimes get more time than other times but oh well.
The only thing I didn't like where the flying dinosaurs. They are very annoying to fight - mainly because when I jump up to hit them I can still get damaged from their bodies. If they only spawned the projectiles and didn't deal contact damage I think they would be way less annoying. I reached wave 5 twice but always died to them (partly skill issue, partly annoyance)
But congrats to you all. A very solid game