While it may be better suited to mobile these days, World of Goo is a great puzzle/bridge-building game with a simple mechanic it explores well.

A seminal masterpiece that took the world by storm with good reason. I spent thousands of hours in Minecraft; a game for me about exploring creativity within tight restriction. Must play.

Kinda unlike anything else. Despite a few technical issues, Cart Life is a really rewarding game about connections and emotions. Great art and music. Challenging in more ways than one.