Hi, thank you for your feedbacks!
As to the difficulty curve, it should get something harder every 10 secs by speeding everything up a little bit. I will look into this and see if I can get a smoother curve. I was also considering lowering the speed again when a hero steals a treasure... not sure how this would affect the gameplay.
And as to the different key to restart... well... this is an entry for the "One Button" game jam, so... :D But maybe I can put a delay before accepting further key input in the game over screen. Thank you for pointing that out :)