3D-SF Cave is a fun little Java applet game that can be played quickly and easily in any Java-enabled browser. Although there is not much to the gameplay, the game's no-frills presentation cuts right to the chase.
The game is played from a first-person perspective, flying through a cave. Walls of the cave are all around, and you control how high or low you travel by clicking the mouse. Click and hold the mouse button to ascend, release to descend. Alternatively, you can use the space bar instead of the mouse button for control. Gravity is added to the formula thus creating a bit of inertia that must be overcome and stabilized to the best of your ability. Hit a wall and the game is over.
Analysis: 3D-SF Cave is a pseudo-3D implementation of a smaller 2D version: SF Cave. Both games were created by Japanese developer Sunflat, and feature just one button control. It is believed that one-button games will herald a revolution in games on mobile devices. I believe that one-button casual games on any platform are among the most successful games at reaching the largest audience possible.
Simple and accessible, no frills, just gameplay. Click.