Yeah the controls are rough at times, specially when doing precise/ little movements.
The undo last block no being there was by design, i wanted the player to feel the weight of putting a block wrong and if they needed to restart that it would be because they messed up, thats why diying to spikes only resets your character and not the other ones.
Yeah the keys were put at the start and didn't iterate on them too much, i agree that S wasn't maybe the best idea ^^"
Thanks for checking it out tho, hope you liked it!