Shattered Pixel Dungeon is incredible, but dangerously addictive. It's the perfect game for a 4-5 hour plane ride -- speaking from experience over the recent holidays.
The only way to break my addiction was to play through it. Due to skill and luck limitations I only got to somewhere in the last 3rd of the game, so I cloned the repo and modified the code so my characters where basically invincible from the beginning and played though it.
