I'm not entirely sure what kind of feudal system encourages knights to mount gigantic birds and whizz around inside a volcano, but it's precisely the kind of bizarre tournament of which arcade dreams are made.
Sadly, the original cabinet of 1982 didn't include a pantomime-style ostrich body to sit inside while playing--but the addictive gameplay was probably enough to keep you (and a pile of change) there anyway.
As one of the ornithologically-based participants in this strange contest, it's up to the player to hop between platforms and fend off waves of increasingly vicious high-flyers with his trusty lance. Striking an opponent from above results in glorious victory (and the chance to snatch a dropped egg to prevent more foes appearing), colliding from below is a ticket to failure. Simple ... but oh so tricky.
The controls, at least, are a doddle. Left and right function as expected and an additional button, when repeatedly pressed, causes the winged beast to beat its wings and take the the air, accompanied by a satisfying flapping sound. Leaving the button alone allows gravity to take over. Dominate the higher air-spaces and your campaign of terror from above can begin.
A second player can also swoop in--both as help and hindrance. Unless a chivalric agreement is reached, your chum is a target like any other; though certain levels award bonuses for keeping out of each others way. Curiously, both ostrich and emu ridden by the players are, in reality, flightless birds. Mind you, they don't tend to carry knights into battle either.
Endlessly ported, remade and showcased online, Joust is as easy to pick up and play as ever. A triumph for outlandish ideas wrapped in basic design, it holds up extremely well.