A game I made with Processing 2 - this game puts the player in control of a massive 'Deathworm', who moves through an infinitely scrolling landscape, eating armed infantry in the desolate environment.
All environmental art, particles, and most of the worm are drawn programmatically in the Processing library. In motion, the vector environment creates parallax, faking 3D.
Physicality was important to the player perception of the control scheme. The worm will skid along the ground when impacting on shallow angles. The worm's head also has a degree of muscular airborne control when segments of its tail are still submerged. Finally, objects respond to the worm when it breaches out of the ground - tanks will flip, and infantry will be thrown, often fatally.
Game elements are shaded in high contrast - splashes of neon colour to indicate ballistics and player mortality. The background elements are flat and and desaturated. This helps visually differentiate the important elements, and also gives the gameplay a snappy feeling due to the high contrast. The background retains a foggier, muted colour palette even throughout the day/night cycle, complementing but not distracting from the foreground.