YOU CAN CHANGE THE TIMES!!!
Maaaan, I spent more than an hour to solve the rocket boots level without changing the times, and I think Stiggstogg did the same. It was only Silv-R Dev's comment that gave me a hint. I didn't understand how could you wait with the rocket boots. And when I restarted I noticed the - + signs.
Why, oh, why you didn't add the button border to those buttons too?
It seems you shot yourself in the foot with the same UX mistake I did with my upgrades.
Then came the bugs. I already noticed one before I knew about the time adjustment options, when the third level got started after the first level, with the to-do list of the second level. This never happened again, so I was fine with it.
But I wanted to play safe. Give me enough time for everything. I reached the part where you have to make the pixel-perfect suicide jump above the spikes right into the small opening between two moving enemies, then another one to get out. I spent there a lot of time. But I was relaxed, knowing that if I can't make the jump, I can still try to fly long enough to reach to other side. I looked at the clock and faced the truth. You can't set any event to more than 10:00.
So I started over and when I finally made the jump, I was resting in the second checkpoint waiting for the rocket boots to finally activate in the right time, at the 9:30 mark, it never happened. It just got striked through and gone. I spent a good 15 minutes to get to that part again, and finally by starting to repeatedly hit the jump 1 minute before the mark I finished the level.
I tried the next level for a few times. Then I took a long look at it, and concluded that this is not my game. To many hazards kill you instantly even though you didn't touch them. I guess because of the rectangular hit box.
I also noticed that if you keep pressing the buttons for a few seconds after you died, you die again immediately. It's not that annoying though, since you lose almost no time.
The sounds are fitting, and I also think, that some music would have been nice. Anyways, that clock noise should be replaced with an actual, animated clock that shows every seconds, not just every 30th second. If you want to keep it, you could still find some music that has some distinctive sound every 30 secs, loops after 30 secs, or puts additional layers on every 30 secs, like a progressive techno song.
Overall, this is a beautiful, polished, almost perfect game. It's just too hard for me, and sometimes not intuitive enough.