Fun game!
The triangle seems to be too useful compared to the other shapes. I almost exclusively used triangle once I got it. It makes the circle almost pointless. Maybe have the circle do something else? Maybe brief invulnerability upon jumping? Or invisibility during a double jump?
I don't like having the restart screen pop up every time I die. There's no penalty for dying anyway, so why not just skip the restart/win screen and just automatically restart/continue? Add a pause button menu with a restart/exit option instead.
The sound effects are too loud compared to the music and are quite harsh on the ears compared to the relaxing music.