+1 to all of these:
- Steamworld Dig (great game, and needs to be played, kind of like Lode Runner on steroids. Dig up secrets, face enemies in the dirt, and upgrade your weapons and tools by finding them. Kind of Metroidy in that respect. I always play through this one when I need something relaxing.)
- Nightsky (roll a ball with a physics engine)
- Gunman Clive 1/2 (2 is harder, but has more beautiful graphics)
- Shantae and the Pirate's Curse (very great, classic platforming and this is from someone who couldn't get into the originals!)