Apparently I'm bad at judging the speed because I've increased it a few times now, but this time I've sped up almost everything (player walk + sprint, balls, cones, kick animations). So hopefully that feels better now!
There is also now a level select which you can get to by pressing escape in a level (or on start-up if you've beaten level 1 previously).
An undo would definitely be great to have, just not the easiest thing to implement with how (badly) my old code is written. So it's not been added yet but I'll see if it's possible to get working in another update.
Thanks for playing!