I don't have too much to criticize about Super Triangle itself - the controls are responsive, the presentation is clean, stage transitions are smooth, the difficulty ramps up at an even pace, I like how the drums seem to beat faster as the game's speed increases, I had fun once I got into the groove and began darting from triangle to triangle - my biggest concern is that the mechanics aren't well-communicated. I almost gave up on trying the game because the instructions refer to the diegetic timer as a "platform beneath" the player. I assumed from this that I could collide with the timer and that there was some form of gravity involved, and so waited for an opening before pressing the space bar. Of course, nothing came of this, and it's only when I took the game's appearance at face value that I started making real progress.
Otherwise, I think the idea of being rewarded for landing at the center of the grey triangles is great and should be expanded upon with some form of scoring system (I wouldn't have even noticed that precision had an influence on the timer if I hadn't read the instructions). I'd probably have played Super Triangle a whole lot more if there was a number counting up my successes, and the added nuance provided by the precision mechanic could've provided greater incentive to play well.
Lastly, and this is a very minor point, the plain "Retry" text clashes pretty heavily with the otherwise minimalistic aesthetic, and I think players would understand how to reset the game well enough without it, since everything is done with just one button.
Awesome job!