I was stuck on now 2nd last level with elefant and the stone and I had no idea that scroll wheel existed and I concluded it was the last level from stepping onto the stone or stepping onto the elefant to see how much levels there were left :D. Now that I've accidentally discovered scroll wheel while trying to remember where I was stuck, now I've completed the entire game :D iirc there were no mention of scroll wheel at the beginning. Also sometimes additionally having controls in the gmae page helps because mid game maybe someone will forget their keybinds.