At the start I had no idea where to click until I accidentally hovered my mouse over the pumpkins. I think a start menu should be obvious.
According to what I've learnt, if you die on the first level there is no way to restart it. Only to reload the whole game.
Now to the gameplay:
Is there any reason to shoot with the mouse instead of a key? It ignores mouse position when you shoot it just seems unintuitive, since if it is the mouse than it usually shoots toward the cursor.
There is a little latency when jumping. But this isn't a big deal since jumping is pretty much useless in this game. You cannot jump over the enemies... So why include jumping then?
Another thing is ammo... Not showing the ammo doesn't make it any more difficult, just annoying. Let alone, you included no sign that the player has ran out of ammo... Or even that there is limited ammo. The fact you didn't give any sign that there is a shop that can be entered by pressing E. Without noticing the shop (Which is pretty well hidden) it just felt like there is a bug in the second wave, that doesn't let you shoot after a while.
However, the graphics looked great, it seems like you have worked hard on it.