I gave Roopit and Boopit another go. Still playing by myself but this time I tried World 5. And how did that go? I got a good laugh when I accidentally smashed Boopit with a boulder! Whoops! I thought it was only fire that kills but I guess not. :O
I was able to get past the first 2 stages of Level 5 playing by myself. Definitely challenging that way, even using the keyboard.
The puzzles are very creative!