Dunkers is basketball played by floppy ragdolls with a single control each. Press to jump and swing; everything else is physics. The result is less a sport than a slapstick contest, which is exactly why it works with two people on one keyboard.
Rounds are quick and the scoring is straightforward — get the ball through the hoop — but almost nothing you attempt goes as planned, which is the joke.
One key per player. Pressing it jumps and swings; the ragdoll physics do everything else, which is what makes it chaotic.
Yes, on one keyboard — that's the intended way to play. A single-player mode against the computer also exists.
Yes — a light 2D game with nothing to install.