Super Hexagon

Probably one of the most important games in the history of this medium. A great triumph of indie gaming over mainstream companies. Keyword: gameplay.

I originally picked up Super Hexagon in a HB Android bundle. As others have said, it looks simple and has a simple idea behind it, but it's actually quite challenging, testing your reflexes and ability to recognize and observe patterns. It also has some rhythm elements to it and the music is fantastic and worth buying as well. It is more suited to playing on a mobile platform, as it's a good time killer and has smooth touch controls, but the desktop version is really not inferior at all. It's simply up to your preference.

Can't get enough.

A simple and entertaining game... on a phone or tablet. The appeal is lost in a desktop format . A game best suited for killing time that can be dropped on the fly, Not so much for the comfort of the desk or couch with hours to spare. Gameplay is smooth and simple. Jusr dodge and escape. In that the game is satisfying and can be rather zen like.

Gotta be on some meth to keep up with even beginning levels.