This game has an awesome potential, also for development, but I found some things that could be improved:
1. At the beginning in the tutorial there is no information on how to kill aliens that landed on the ground from the destroyed spaceships, I tried to run on them (but I have no pistol), to hit them with a cannon and accidentally I found out that you simply need to jump on them;
2. Something that needs fixing: with the mouse aiming on, every time when I am using a cannon and I try to click on menu or the next wave button I am also shooting, losing ammo;
3. For these levels end modes, maybe more medals? Like halfway there in one mode or for the number of enemies shot down?
4. For me, the man could move a bit faster and maybe some improvement of the jumping, now it looks like we are on the moon with low gravity, or we are using a jetpack ;-)
5. Maybe some upgrades during the game for the cannon or for the turrets?
But nevertheless it is already a piece of a great job!