Card Monsters lets you play a creatures, instants, and sorceries. You to play the game against a computer-controlled opponent. Currently there are over 300 cards, and you can play in constructed, sealed, and draft mode. The program can automatically download all of the card pictures. The GUI is basic but very usable.
ChangeBlindness is a small game that demonstrates the change blindness phenomenon. The effect shows that our brains have a low-level (i.e. subconscious) change detection capability that can be disabled pretty easily (for instance, with a flicker of around 100ms). The game illustrates this using an increasing number of icons, one of which will change during a flicker. The goal of the game is to find the changing icon as quickly as possible.
Superficially, Dominoes on Acid is a solitaire variant of Dominoes with weird colorful tiles (and this view is enough to play the game). But on a deeper level it is a GUI for natural deduction. Every completed domino is equivalent to a proof of a tautology in classical propositional logic. The game can be played online as an applet or offline as an application. It is built on a simple isometric engine that can be used independent of the game.
Fox Hunt is a logic game written in Java. It was inspired by the sports competition of the same name. In that competition, participants run in the forest equipped with small radio locators, seeking small hidden radio wave emitters called "foxes". In Fox Hunt you are one of such participants armed with advanced locator which can scan full horizontal, vertical, and both diagonal directions and report the number of foxes "visible" at all these directions.