Good job on the game! I like the idea of the game, having the unique abilities S1-S4. Down below is some feedback for yeah.

Feedback:

• I enjoyed the power system, but I did not like that I had to click them each time to do something. (Or maybe I forgot to see an instruction). I think something that might be nice to do is hotmap them to the top number row of the keyboard.
• Similar to what NeatGames said I think if you added some upgrade system and tied those in with powers you already have it would make for some interesting gameplay! :D
• For bullets, a bit picky from me, but could make them slower than the player movement. Personally, it was kind of weird how I could catch up to them. 
• Some particle effects on enemy death, projectile and some time delay on when enemy getting hit would improve game feel a bit.
• When enemy waves spawn, sometimes I don't see them for a bit because I am moving around a lot. Potentially add a mini map so I can see where enemies are, or maybe have off screen indicator to tell where enemies?

• Overall: The game was really cool and I like the special abilities! I wish I could just hold down the button to shoot, and not click click click hehe.
• Fun: It was a lot of fun to control and avoid enemies. I like the clone ability the best.  If you add rogue-lite upgrades you could do a lot of cool upgrades for the them, like more clones spawn
• Visuals (Graphics): Great start! Some simple squash and stretch animations on the sprites would help it look more lively in an easy way.
• User Interface: Looks like it is still WIP. Just some simple transparent button sprites would look better~ and then add some spell icons later.
• Audio: Adding some subtle foot step sounds when the player moves would be nice.

Great job making a cool little game, keep it up! Please check out my game when you have time :D