Jump King is a simple, brutal, bastard of a platformer in which you attempt to steer a king towards the top of a single tower using his chargeable jump. Misjudge a particular jump by over- or undercharging it, maybe bounce back off a wall, and you may find yourself tumbling all the way back to the beginning again.
It's probably about to get a bunch of even harder levels, however, because nearly five years after release it has just got Steam Workshop support and a new set of modding tools.