Its a fine platformer, I liked the art style and the controls are quite solid
I found these 2 bugs:
1) If you grab the key in the first level, quit the level and replay, you start with the key grabbed.
2) I died in the first level inmeddiatly after grabbing the key, and 2 screws spawned on the left instead of 1. After grabbing all the screws (plus the extra) I finished the game with 16 screws (instead of the usual 15), and got the "not enough screws" ending.
Also, some things to consider. You dont make it clear enough that you have to grab the screws AFTER grabbing the key.
Which takes me to the rewind. It doesnt feel like a rewind, but more of a change of scene.
You should try adding some sound effects (like Jump, pickup, and pad sounds). Check out BFXR for free sound effects.
Finally, I dont like that the player is just a white circle, since it stands out a lot in comparisson to the rest of the Art style. You should either try to make the rest of the artstyle more simple, to fit in with the player, or make the player more complex to fit with the rest of the scene (I think a robot would work really well, since you seem to be in a factory collecting screws).
Overall Its a good game, Well done :D