Nitrome's second entry in their 50x50 pixel experimental series requires you do a very simple thing: Listen to a Van Halen song for six hours straight. Study its words. Heed its message. Don the hairdos. Only when you master the song are you able to fully understand the nature of J-J-Jump, a fast-paced platformer with a light puzzle twist. (Note: Van Halen not required.)
As the flood waters rise beneath you, you've got to climb the towers using the [arrow] keys and avoid enemies and obstacles to reach the flag at the end of each level, generally somewhere above your starting point. Yes, jumping is a major part of your ascent, as well as double-jumping and triple-jumping and beyond, but there's a restriction to make the game just a bit more interesting. At any given time, you're allowed to use the [up] key to make jumps only five times. Your remaining jumps are indicated by the arrows at the bottom of the game. You can restore your stockpile of jumps by picking up flashing orbs and passing by checkpoints, but you've still got to ration your jumps carefully to make it to the top. (Jumps made by springboards will not count against your stockpile.)
The tiny size may not be the best playing environment for a game where precision movements are key (particularly in later levels when you have to weave in and out of enemies), but it works well to illustrate that it's definitely possible to cram a quality game into such a small space. If you want a quick challenge, you might as well jump!