Point the mouse where you want to jump and press space. Touch red and restart the level, or green to go to the next level. It's a platformer; you know how to play.
This was made for an old Scratch Codegolf and as such it is a little glitchy(eg. floating slightly, occasionally safely landing on red). All the levels are possible. If you really get stuck, you can drag the character. Altogether the blocks in the project as you see it count to 28 Blocks. The essential workings needed to pass the challenge use only 13 Blocks. With those blocks you can jump around but there are no levels or respawning. It takes 11 more blocks to make it actually fun, plus 4 more for the flag to restart at level 1.