Level design is probably one of the biggest challenges to any game I've tried making, however I hope it will get better with time and practice! There is a plan to add many more levels and boosts in future for this particular game and I sure hope that will make it more interesting than it is now.
About triangles movement, it was an intention as that way player has to explore, a game, that isn't really long at all. Saying these things at the beginning would probably just spoil the game that has not a lot of content anyways. There was also an issue of balance - not to easy not to hard.
E ability does appear, but the chances are randomized by a certain algorithm(feel free to check out source code for more explanation but keep in mind that the code might feel a bit messy - or at least it feels like the for me). So the only way to find that E power up is to play more(therefore increasing chances of being the right "seed" for an ability). Thanks for playing!