Well, I got to 2:49 eventually. Not sure if I can shave off another five seconds, though. I feel like I must be doing one of the levels with an imperfect strategy.
Turns out I was doing levels eleven and sixteen wrong. I got back four seconds from sixteen and one from eleven.
For those trying to get the medal, here are the times I earned on each level:
1: 2s;
hold right
2: 3s;
hold right
3: 3s;
falter slightly before moving right
4: 4s;
remember to grab the yellow shroom go right once you can
5: 6s;
6: 5s;
ignore shrooms
7: 9s;
8: 7s;
don't wait for the spider after getting the fireshroom
9: 10s;
10: 12;
11: 4s;
right, up, r, u, r, down, r, u, left, d, l, u, l, d
12: 5s;
r, d, r, u, r, d. get ice shroom, make one ice block to the left, get blue shroom
13: 8s;
reminder, ice balls go thru spikes
14: 9s;
15: 6s;
r, u, r, d, r, d, r.
16: 4s;
l, r, d, r, u, r, u, l, r.
r, d, r, d, l, u, l, r
not sure which is faster
17: 11s;
18: 18s;
19: 1s;
hold left until right
20: 22s
I keep thinking that there must be a faster way that skips a walk cycle, but I haven't found one.
Aha! go to the left through the portal, then to the right to get the key, then back through the portal, then to the right. you can skip one walk cycle. thank you HerbieG! this was a good challenge
In game total: 2:38(164s)
https://www.newgrounds.com/dump/item/2981be36f13a4cd4f9786095fd70ed79
My sum: 2:29(149s) I guess it rounds down