Cool concept and looks good.
It would be nice to have a button to retry a level, like press R to instantly die and restart.
In level 2, I couldn't jump high enough at first. I changed my display to 30Hz and then I jumped much higher, so I could beat all 3 levels. While the movement speed per frame should change with fps, the total height shouldn't. If you use delta_time to integrate the speed from acceleration, you also have to do the same for integrating position from speed. So v += a*dt, but also x += v*dt.