Hey
I liked your game. You've done a great job tutorializing / showing the mechanics progressively. (first advance the the coin on a flat ground, then jump and place a platform at the same time, then more difficult situations).
For improvements, I think the player should be able to recover when they fall. For example by placing a platform directly under them. Right now the platform can only be placed slightly in front of the player, so you can no longer land on a platform you place when you're already falling fast.
Congrats for your game!