If there is a door across a corner from you, and a key normally blocking that corner, you can sometimes unlock the door before collecting the key. Demonstrable in (Base64 for endgame spoilers) MC01, just hold right as you jump up after the tall black door.

I find it a bit annoying that when you walk a bit, do something and then undo, you get teleported all the way back. It would be nicer if you would be teleported back to the last valid standing location instead of the first one after the last action. I figure this can be changed by putting the player position onto the undo stack last and swapping it out as long as you are on a valid standing location. Also, touching salvage points should be an undoable action, which it currently isn't. Additionally, there is a bug where, when you did an action but are not in a valid location (like within a salvage point), you can't undo. Also, why do you need recentPush? Isn't recentPush always 1 once you pushed an undo stack frame? I mean, after every undoPOP call you eventually call undoPUSH, so recentPush will necessarily be 1.

You can cheese omega-9 by not hitting the purple blank door on the 0 bypass route to swap glitch and going in with white instead, causing you to shift orange but not cyan.

My game is quite often unfocused (on Windows), but when I click on it for it to be focused again, the pencilmark menu opens every time, which is pretty annoying. Maybe there is a way to detect if the game is unfocused on Windows, so that the pencilmark menu doesn't get opened in that case?

If i have to remember the setup for Stable Loop one more time i am going to have an aneurysm

Unsure if just weird intended behavior or bug, but: (rot 13) jura cynlvat guebhtu jbeyqf 1-5, v arire fxvccrq n (ahzorerq) yriry, ohg va jbeyq 6 v fxvccrq yriry 3 (v hfhnyl cynl va beqre, ohg v jnf fgvyy jnxvat hc), naq nf n erfhyg yriryf 7, 8, naq 9 bcrarq hc, ohg abg yriry 6. v nffhzr vg'f whfg n dhvex bs ubj gur yriry haybpx flfgrz jbexf gung v unqag abgvprq gvy abj, ohg gubhtug v'q ercbeg whfg va pnfr.

Post T4 Spoilers:

V guvax vg jbhyq or n ernyyl avpr nqqvgvba vs lbh pbhyq erfrg qbbef gb ubj gurl jrer orsber nal zbqvsvpngvba va gur Bzrtn Grezvany. Pheeragyl, lbh unir gb erqb gur fnyintr gb oevat gur qbbe onpx naq vg'f ernyyl naablvat univat gb erqb G2-7 guevpr rirelgvzr lbh guvax lbh zbqvsvrq gur qbbef jebat.

When I hit the "defaults" button in the sound options, the balance changed from its initial values.

When I changed the color of keys/doors, they didn't update until I quit and re-entered the level.