Use [WASD] to move around, and [R] to interact with doors, switches, and elevators. If your jump doesn't have quite enough oomph to reach the top of a ledge, Roy may grab hold of the edge so you can tap [W] to climb up. Press the directional button towards the walls when you fall to wall-slide, letting you slip slowly downwards so you can find out if safety or a toothy death awaits. Your hero has three colours to choose from that change his abilities, making you a limited but awesome one-man Power Rangers team, and you can swap between them with ease by using the [J], [K] and [L] keys or just clicking on the screen. You can even do this in mid-leap; handy, considering certain platforms require you to be a certain hue before they'll support you.
Each colour has its own special ability that can help you out in the right situation. Blue can conjure blocks of ice to use as stepping stones or weigh down triggers, while red can let out of a blast of flame to damage enemies. Yellow can turn invisible and avoid most damage, but renders you unable to move until you become visible again. (And also activate checkpoints when available by pressing [R]!) Each of your colours will be upgraded once as you progress, adding new abilities. You'll have to learn to use not only the environment but your abilities to your best advantage if you want to survive. Just be careful, since one wrong move and your colourful butt is burnt toast.
Analysis: In my staggering ignorance as a player of games rather than a creator thereof, I feel confident in saying that it's pretty easy to make a platformer, but difficult to make one that doesn't have that distinctive plumber aftertaste. (Which is to say, greasy and hairy.) Primary juggles both its puzzling and its platforming admirably, and manages to make a distinct experience where you don't feel as though a hedgehog or a bandicoot could have been substituted for the same effect. The game's presentation is also wonderful, from its sticky enemy design to the music that changes subtly with your hero's chosen colour.
In fact, Primary's biggest enemy may be its awkward control set up. I have no problem with the [WASD] concept, but tangling the other action keys around those doesn't exactly make for smooth gameplay when your fingers are fumbling around each other. I also question the use of the insta-kill; yeah, okay, there are checkpoints and the levels are typically small by design, but considering how easy it is to misstep around the countless lasers, enemies, and gooey black death floors you'd think a 3-strikes hit rule wouldn't be unreasonable. Seeing the achievement for 25 deaths pop up while I was futilely battering myself against a boss was just insult to injury.
Thankfully, the controls do become more intuitive as you go along, and before long you'll be a colour-swapping champ. To prove it, you can even tackle some of the achievements that don't involve dying painfully, and track down every special crayon hidden throughout the game for extra points. (I always knew you were a few crayons short of a full box.) Despite its shortcomings, Primary is still a clever, fun, and challenging way to spend an evening. So go on. Get out there and save Huemanity.