[PC, Steam] Islands of Insight $26.37 (40% off) @ Steam

I am really enjoying this MMO puzzle game which released last month and is now discounted as part of the Steam Spring Sale. Walk , jump and fly around pleasant scenery and stop to solve a variety of puzzles along the way. Puzzles range from very easy to extremely hard but you can pick the ones you want to do from over a dozen different types. There is a skill tree and cosmetics to unlock. You can complete daily quests and there is even a meta-quest involving some tricky puzzles.

Puzzles are single player only, but you can see other people moving around the world and wave hello.