So, I've been using the transitioning glitch i posted in another thread, and boy it is overpowered. After i managed to do it consistently, i just did a practice speedrun, but i did the unthinkable and pulled off a 11 minutes, 58 seconds and 840 milliseconds. That's a new WR, unless if i didn't record or took a screenshot... in which i took none. Check my guide so we can do the first 11 minutes.

If you play classic, 1-8 to 1-21, this will help you. There is a glitch that if you beat a level, you can press esc in a kind of frame perfect stage, while the "Level complete!" is still on screen, and you will exit the level instead of doing nothing. it still counts, because the menu is on the stage, just not on screen. if you do it correctly, you have saved about half a second. Good for 12 minutes 0 secs runs. Anyway, if you do it, while the screen is still black, if you press the right arrow, you will go on the menu on already the next level. just wait about 0.3 seconds and press space. If everything is done correctly, you should save 1 second and 200 milliseconds from each level. Imagine the difference on a 21 level run. Good luck trying to pull it off, i have done it in my 21st attempt.