This game is suuuuuper fun! For your first game, it is an outstanding effort. Congratulations on getting it done in time!
The mix of platforming and topdown levels is an interesting concept! I can imagine some cool animations happening between the levels, showing the camera moving from side-on to a bird's eye view.
The first level is fun and I like the variety of speeds with the enemies, maybe you could have different colored enemys for different speeds? It Reminds me a lot of the world's hardest game.
The second level is quite challenging, and I got a large amount of satisfaction once I completed it. (One thing I noticed is the money sprites looks blurry, make sure to turn off compression in the import settings for pixel art in Unity!)
The final level is an entertaining platformer with a camera that handles well. It has a layout that is fun to navigate and traverse. The next obstacle is nearly always in view before the player gets to it, which makes it feel very fair.
I didn't seem to notice the fullscreen issue you mentioned on my 21:9 monitor, so that's a plus.
Again super well done and we hope to see more games from you in the future, even an update to this game with some more levels would be awesome! :)
P.S if you want to turn off the Unity WebGL border for the build go to Edit > Project settings > Player > Resolution and presentation > click the minimal template :).