World 4 done. About 980 frames saved over EightBitGuy in this world.
Non-trivial improvements:
-- 4-2a, duck-turning with the key saves 2 frames. This let me beat an apparent frame rule with the conveyors, saving 8 more frames during the backflip.
-- 4-2b, I found a faster way to ascend the donut platforms, saving 37 frames.
-- 4-6a, a new trick allows pressing the yellow switch without having to go all the way around, saving 920 frames.
-- 4-6b, somersaulting at the end saves 11 frames.
The new trick involves starting a handstand and alternating left and right every frame at the apex of the jump. For whatever reason this levitates Mario in midair and makes him slowly rise at 9 speed. I discovered this while messing around in 3-4a trying to glitch Mario through the red blocks above the pounder. (Turns out it's possible, but it takes way too much time to execute.)
9 speed is extremely slow - about two pixels per second. For comparison, running is 272 speed and jumping starts out at 627 speed. On top of that, the handstand jump is quite short (about one block height, compared to the backflip's three-ish blocks) so it takes forever to gain any meaningful height with the trick. If there's a platform that backflipping / somersaulting can't reach, it'll almost certainly be faster to do the level normally than to spend 30-40 seconds getting up there with the trick. So while you
can use it to ascend as high as you like, I don't think it ever saves time to do so.
The more-useful aspect of this trick is that you get to hover in midair indefinitely. In 4-6a I use the trick to press against the underside of a donut block, which you can't do normally, in order to activate it from the wrong side. Unfortunately there aren't many situations like this in the game so I wouldn't be surprised if this is the only place the trick is useful.
