First of all, great job on your first submission!
For improvements: There are some obvious things missing for example, adding music / more sound effects and some kind of instruction / introduction for the player to get started. Otherwise, the maps are designed quite well, though I'm not sure what level 3 was supposed to be, I simply jumped around the wall (or was that the thing?). Like others have mentioned, the sensitivity of the mouse movement could be tweaked a little lower.
It's a good foundation to build and improve upon. Nice for first submission when you're still young!