Your goal is to gain as many points as you can within the time limit. You gain points from your speed which gradually increases over time. Careful though, if you hit the spikes, you "die" but instead of travelling to your death state, you simply end up in a slightly warped mirror of reality. Hit another spike and you return.
Hitting spikes will also significantly reduce your speed so it is best to avoid them at all costs! There is no penalty from being in the mirrored plane apart from the initial reduction in speed from hitting the spikes so don't worry too much.
Do whatever you must to avoid the spikes, Jump with the Spacebar, Speed Up with the Right Arrow and Slow Down with the Left Arrow. Press R to return to the time selection screen. Grind along a platform if you are daring enough but be warned, you may hit your head and experience signs of concussion if you attempt to jump into the bottom of a platform.
Post your best score for each different time limit and see if you can be the best of the best.