If you were a gamer in 2007, you remember Portal. For those unfamiliar with the award-winning game, it uses a special physics engine developed by Valve (who also published the game) in order to work your way through a maze of puzzles. People have been wanting the game to come to mobile platforms for years and starting on May 12th, that will finally happen.
For $10 (which is comparable to the price on other platforms), the original Portal is a great game. You have to wait until May 12th for it to launch on Google Play for the Shield, but you will definitely enjoy it.
Source: Android Central