XorCurses is a game based entirely on Xor by Astral Software. The original game was released around 1987 for the 8-bit home computers popular at the time. XorCurses attempts to faithfully recreate that game for Linux, but slightly ironically, uses ASCII characters instead of pixel based graphics (which even the 8-bit computers could manage). The idea of Xor is to roam around a series of mazes collecting masks. The first level is simply a matter of finding your way around, but the second level introduces fish and chickens which block your path or kill you if they hit you. From there on in, things get progressively tougher and really is a challenging and difficult puzzle game.
HexGlass is a Tetris-like puzzle game based on a hexagonal grid. Ten different types of blocks continuously fall from above and you must arrange them to make horizontal rows of hexagonal bricks. Completing any row causes those hexagonal blocks to disappear and those above move downwards. The blocks gradually fall faster and the game is over when the screen fills up and blocks can no longer fall from the top.