This shape uses 17 pieces in total. Acmlm used 18 pieces to reach his first tetris in published TAS. Estimated improvement about 25-30 frames.
"Tree#1" must have 15 blocks high and have 3 blocks flat top (it is T, L, or J tetraminos.) At the right branch two blocks at rightmost down corner must be empty. Last piece to burn tetris is L.
SRNG - Starting RNG
It is possible to try take extra advantage of using different starting RNG if to start at other frames. If find lucky starting RNG maybe some additional frames can be saved. Estimated improvement about 0-10 frames.
CH18/CH19 - Chessboard build
Instead of doing one long hole is better to build chessboard with knee after each 4 layers.
It allow burn faster becouse of long "I" tetramino will travel for shorter distance to ground.
At level 18 speed "Chessboard build" can save 48 frames (8 + 16 + 24)
At level 19 speed "Chessboard build" can save 40 frames (7 + 13 + 20)
T3Skip - Tree#3 skip
Tree#3 can be skipped completely. It mean we need five full teramino less! So it will save about (25-30) * 5 = (125-150) frames.
To do so after transition we do not burn all field, instead of tree#3 is possible to use 12-lines ground.
HBB - High Build Bonus
Additional betefit of skipping Tree #3 is that possible to continue building immidetely after transition. See picture above. I dont estimate how much it will save, lets say about 10-20 frames.
EM - Extra movement
There is a pausing trick that allow to move teetramino to one extra block futher than expected normally.
This trick not used in previous TAS. Not sure will it save something or not. But at least we have more freedom for build.
EIE - End imput earlier
End of imput can be done as soon as last "I" tetramino is rorated. Estimated improvement about 65 frames.
Well, it is not pure improvement it is more alternative ending timing method. After reaching 999999 points Acmlm also reached top of screen to finish game faster. But i disagree this this decision, in my opinion shortest input time is universal goal for all TAS. And so Tetris should not be an exception of this rule.
EP - Ending problems
Besides pros, my new strategy has one serious difficulty at the very end.
For perect ending we need 4 long pieces "I-I-I-I" in row at very end. It is extrimly difficult to achive.
EP0 - I think if re-solve last segment many times sooner or later right RNG with 4 "I" at the end can be found.
For case if it would be impossible (or too long) to get 4 "I" there are two possibility:
EP1 - It possible to waste one piece like I-X-I-I-I or I-I-X-I-I or I-I-I-X-I
But i strongly not like idea of wasting piece. EP1-solution is not an option for good TAS.
EP2 - To avoid wasting piece there is alternative "smart end" by using incomplete upper tetris: it require only long pieces "I-I-I" in row.
For example like this. I-O-O-I-I-I. Or something similar. It slower than 4 "I" but 3 "I" seems more or less possible to achive.
Estimated worsening for EP1/2 about 25-50 frames.
Summary:
IMP = FT + SRNG + CH18 + T3Skip + HBB + CH19 + EM* + EIE - EP
(25-30) + (0-10) + 48 + (125-150) + (10-20) + 0* + 40 + 65 - (0/25-50) = 263-373 frames can be saved +/- something.
Playaround
I also think that would be nice to improve not only "fastest 999999" but also "playaround" and beat both remaining TASes at the same time.
To do so after completing "fastest 999999" with improvement we will dont stop here. No! Instead we start doing bonus "playaround" and play additional 2-3 minutes. For playaround my idea is to draw pixel art.
Pixelart1 -> Burn -> Pixelart2 -> Burn -> Pixelart3 -> Burn -> ...
Final product can be called "fastest 999999 + playaround" or simply "Mode A". But it too early to discuss. Since fastest 999999 is the hardest part.I made this easier by bruteforcing again! Overall, it went like this: Find all possible ways to fit blocks into each side (or as many as I can, I got a few dozen) Get the player input for each of them (and how many frames it takes to place each block) Also get the input to delay the next block by any amount of frames (up to about 10, and pausing when left+right+down isn't enough) Using the above, code the bruteforcer in C, and use it for a (mostly) easy ride to level 19 and above And the bruteforcing: (instant, too) Go through each left/right block sequence (for a single tetris), and each way to alternate sides For each of them, find how long it'd take to manipulate and place all blocks Keep the shortest one, display it and generate .fm2 data to copy-paste into the run
I'm not sure just how long a list of valid piece orders would be though (especially since, with your chessboard build, if i'm understanding it right, each of the 10 different spots we could place our hole on the fourth row would be a totally different set of usable piece orders).
It would be nice to get access to those lists of "left side" and "right side" valid piece orders as a base. I wonder how many more could be found.
seq[6][1] = { {I, O, O, I, I}, {L, Z, Z, T}, {J} }
frm[6][1] = { {x, x, x, x, x}, {x, x, x, x}, {x} }I-J-Z-J-I-I
I-J-I-Z-J-I
I-J-Z-I-J-I
Ah, that's interesting, that because of the shift in the fourth row's gap, an I block is now a valid choice for doing a triple-tetris. Does the top block actually end up left over? Normally any blocks off the top cease to exist once the piece is placed, but I could see this triple-tetris being a special case.
Actually putting the blocks in will be annoying
J-J-Z-T
J-J-Z-Z
I-I-I-I-L-L I-I-I-L-S-L I-I-I-J-S-L
X-X-X-X-X-X X-X-X-X-X-X I-I-J-I-S-L
X-X-X-X-X-X X-X-X-X-X-X I-J-I-I-S-L
X-X-X-X-X-X X-X-X-X-X-X J-I-I-I-S-L
I-L-L-T-T-L I-L-L-I-L-L I-L-L-J-S-L
T-I-L-L-T-L X-X-X-X-X-X X-X-X-X-X-X
I-T-L-L-T-L X-X-X-X-X-X X-X-X-X-X-X
I-L-T-L-T-L X-X-X-X-X-X X-X-X-X-X-X
I-I-I-T-T-L I-I-L-L-L-L I-I-I-J-O-L
I-I-T-I-T-L X-X-X-X-X-X X-X-X-X-X-X
I-T-I-I-T-L X-X-X-X-X-X X-X-X-X-X-X
T-I-I-I-T-L X-X-X-X-X-X X-X-X-X-X-X
I-I-O-O-L-L I-I-L-Z-Z-L I-I-I-J-Z-L
I-I-L-L
T-T-L-L
T-L-T-L
T-L-L-T
S-S-L-L
S-L-S-L
S-L-L-S
I-J-Z-J
I-J-J-O
I-J-S-L
I-I-I-I-I-I I-L-L-J-J-I I-I-J-L-O-I I-I-J-J-L-L I-J-Z-L-I-I I-I-I-J-O-L
X-X-X-X-X-X L-I-L-J-J-I X-X-X-X-X-X X-X-X-X-X-X I-J-Z-I-L-I X-X-X-X-X-X
I-I-O-O-I-I I-J-J-J-J-I I-I-O-L-L-I I-L-L-O-L-L I-J-T-T-I-I I-I-L-J-J-I
I-I-O-I-O-I X-X-X-X-X-X X-X-X-X-X-X X-X-X-X-X-X I-J-T-I-T-I X-X-X-X-X-X
I-O-O-I-I-I I-I-I-J-J-I I-I-L-O-J-I I-I-I-O-L-L I-I-J-O-L-I I-J-J-O-I-I
I-O-I-O-I-I X-X-X-X-X-X X-X-X-X-X-X X-X-X-X-X-X X-X-X-X-X-X I-J-I-J-O-I
I-O-I-I-O-I X-X-X-X-X-X X-X-X-X-X-X X-X-X-X-X-X X-X-X-X-X-X X-X-X-X-X-X
I-I-I-O-O-I I-O-O-J-J-I I-I-J-O-J-I I-I-L-I-T-L I-I-J-Z-J-I I-I-J-J-O-I
I-I-O-I-O-I I-O-J-O-J-I X-X-X-X-X-X I-L-I-I-T-L X-X-X-X-X-X X-X-X-X-X-X
X-X-X-X-X-X I-O-J-J-O-I X-X-X-X-X-X L-I-I-I-T-L X-X-X-X-X-X X-X-X-X-X-X
I-J-J-I-I-I I-I-J-J-I-I I-T-T-J-I-I I-I-T-T-L-L I-I-L-T-T-L I-I-T-T-J-L
X-X-X-X-X-X I-I-J-I-J-I I-T-T-I-J-I X-X-X-X-X-X X-X-X-X-X-X X-X-X-X-X-X
X-X-X-X-X-X X-X-X-X-X-X I-T-I-T-J-I X-X-X-X-X-X X-X-X-X-X-X X-X-X-X-X-X
I-L-L-I-I-I I-I-L-L-I-I I-T-L-T-I-I I-L-L-J-I-L I-I-L-Z-J-I I-I-L-T-T-L
X-X-X-X-X-X I-I-L-I-L-I L-I-T-T-I-I I-L-J-L-I-L X-X-X-X-X-X X-X-X-X-X-X
X-X-X-X-X-X X-X-X-X-X-X I-L-T-T-I-I X-X-X-X-X-X X-X-X-X-X-X X-X-X-X-X-X
I-I-T-L-T-I I-I-J-Z-J-I I-L-S-L-I-I I-I-T-T-J-I I-L-Z-I-J-I J-I-I-I-I-L
I-I-T-T-L-I X-X-X-X-X-X I-L-S-L-I-I X-X-X-X-X-X I-L-I-Z-J-I I-J-I-I-I-L
X-X-X-X-X-X X-X-X-X-X-X I-L-I-S-L-I X-X-X-X-X-X X-X-X-X-X-X I-I-J-I-I-L
X-X-X-X-X-X X-X-X-X-X-X X-X-X-X-X-X X-X-X-X-X-X X-X-X-X-X-X I-I-I-J-I-L
I-L-L-L-L-I I-I-J-S-L-I I-J-Z-J-I-I I-I-L-L-I-I I-I-L-O-J-I I-I-I-L-S-L
X-X-X-X-X-X X-X-X-X-X-X I-J-Z-I-J-I X-X-X-X-X-X I-L-I-O-J-I X-X-X-X-X-X
X-X-X-X-X-X X-X-X-X-X-X I-J-I-Z-J-I X-X-X-X-X-X L-I-I-O-J-I X-X-X-X-X-X
I-L-L-I-I-I I-L-L-O-O-I I-I-L-S-L-I X-X-X-X-X-X X-X-X-X-X-X X-X-X-X-X-X
I-L-L-T-T-L I-L-L-I-I-L I-I-J-J-O-L
I-L-T-L-T-L X-X-X-X-X-X J-I-I-J-O-L
I-T-L-L-T-L X-X-X-X-X-X X-X-X-X-X-X
T-I-L-L-T-L X-X-X-X-X-X X-X-X-X-X-X
I-I-T-T-Z-L I-I-I-I-I-L I-I-J-J-Z-L
I-T-I-T-Z-L X-X-X-X-X-X J-I-I-J-Z-L
T-I-I-T-Z-L X-X-X-X-X-X X-X-X-X-X-X
I-I-I-T-T-L I-I-L-L-I-L I-L-L-S-S-L
I-I-T-I-T-L X-X-X-X-X-X X-X-X-X-X-X
I-T-I-I-T-L X-X-X-X-X-X X-X-X-X-X-X
T-I-I-I-T-L X-X-X-X-X-X X-X-X-X-X-X
I-I-L-L-Z-L I-I-O-O-I-L I-I-I-S-S-LSo, you did verify all these are actually possible at Level 18 speed to build? (Some only with Pausing probably.)
And a R+0 has to go with L+1, and vice versa. I see... Evidently it's extremely convenient for the +1 to be on the final I piece in this hole setup.
I'll try and get something going some time soon, my life is very odd at the moment...
By the way, I'm not really down with the "obsolete the playaround" part, it's a bit odd to combine the two goals for one, and also playaround TASes in general don't feel like something that should be obsoleted. They are, often literally, art.
I-I-O-J I-J-Z-T I-J-T-T
J-J-O-J I-T-Z-J I-T-T-J
I-L-L-J L-Z-Z-T L-Z-T-T
I-J-S-O I-L-S-O I-O-S-J
I-J-I-T 
Note: It the same list of cases as part of L+1 list for hole#10 where "I" piece was used at the end, only now with "J" at end instead. 
I-I-I-I I-J-S-L L-L-L-L I-L-L-O
I-I-O-O I-J-J-O L-Z-Z-L I-L-O-J
J-J-I-I I-J-Z-J I-I-L-L I-L-S-L
J-J-O-O L-Z-J-I O-O-L-L I-L-S-L
I-J-J-I L-Z-T-T J-J-L-L I-O-J-J
I-T-T-J I-T-T-L I-J-Z-L I-J-T-T
Note: It the same list of cases as part of L+1 list for hole#10 where "L" piece was used at the end.
I-J-S-O{"I","L","Z","L","L","O","O","Z","T","J"}: 28 ({7,2,0,0,5,3,0,5,4,2})
{"I","L","Z","L","L","O","Z","O","T","J"}: 26 ({7,2,0,0,5,3,3,0,2,4})
{"I","L","Z","L","L","O","Z","T","O","J"}: 25 ({7,2,0,0,5,3,3,1,3,1})
{"I","L","Z","L","L","Z","O","O","T","J"}: 35 ({7,2,0,0,5,2,1,14,3,1})
{"I","L","Z","L","L","Z","O","T","O","J"}: 25 ({7,2,0,0,5,2,1,6,1,1})
{"I","L","Z","L","Z","L","O","T","O","J"}: 26 ({7,2,0,0,0,5,2,8,1,1})
{"L","I","L","L","O","Z","O","Z","T","J"}: 35 ({0,5,1,12,11,2,0,1,2,1})
{"L","I","L","L","O","Z","Z","O","T","J"}: 43 ({0,5,1,12,11,2,1,8,0,3})
{"L","I","L","L","O","Z","Z","T","O","J"}: 38 ({0,5,1,12,11,2,1,0,2,4})
{"L","I","L","L","Z","Z","O","O","T","J"}: 45 ({0,5,1,12,2,11,6,6,1,1})
{"L","I","L","L","Z","Z","O","T","O","J"}: 41 ({0,5,1,12,2,11,6,0,4,0})
{"L","I","L","L","Z","Z","T","O","O","J"}: 59 ({0,5,1,12,2,11,9,1,13,5})
{"L","I","L","Z","L","O","O","Z","T","J"}: 29 ({0,5,1,2,3,7,0,5,4,2})
{"L","I","L","Z","L","O","Z","O","T","J"}: 27 ({0,5,1,2,3,7,3,0,2,4})
{"L","I","L","Z","L","O","Z","T","O","J"}: 26 ({0,5,1,2,3,7,3,1,3,1})
{"L","I","L","Z","L","Z","O","O","T","J"}: 36 ({0,5,1,2,3,6,1,14,3,1})
{"L","I","L","Z","L","Z","O","T","O","J"}: 26 ({0,5,1,2,3,6,1,6,1,1})
{"L","I","Z","L","L","O","O","Z","T","J"}: 27 ({0,5,3,0,5,3,0,5,4,2})
{"L","I","Z","L","L","O","Z","O","T","J"}: 25 ({0,5,3,0,5,3,3,0,2,4})
{"L","I","Z","L","L","O","Z","T","O","J"}: 24 ({0,5,3,0,5,3,3,1,3,1})
{"L","I","Z","L","L","Z","O","O","T","J"}: 34 ({0,5,3,0,5,2,1,14,3,1})
{"L","I","Z","L","L","Z","O","T","O","J"}: 24 ({0,5,3,0,5,2,1,6,1,1})
{"L","I","Z","L","Z","L","O","T","O","J"}: 25 ({0,5,3,0,0,5,2,8,1,1})
{"L","Z","I","Z","L","L","O","O","T","J"}: 36 ({0,0,2,0,2,14,3,11,3,1})
{"L","Z","I","Z","L","L","O","T","O","J"}: 26 ({0,0,2,0,2,14,3,3,1,1})
{"L","Z","I","Z","L","T","L","O","O","J"}: 10 ({0,0,2,0,2,0,1,1,2,2})And I'm still unsure if I should try to code a way to do the inputs automatically. It'd probably save time in the long run...
To have inputs automatically it can be very useful. In this case we be able to apply even deeper optimisation methods. Recurrent multi-tetris optimisation: It would be possible to try minimize average delay for several tetrises by better conjunction between them. For example if for one tetris delay is small 10 frames, but delay for next one is long 37 frames. 10+37=47. We can check second best option 26 delay for first tetris and look what delay for next tetris it can be like 13. So 26+13=39 summay delay is lower = better. And so on for each tetris conjunction. Or even minimize delay for several tetrises D_min(D1+D2+D3+Dn). Well of course we try to do the same without inputs automatically too, but to do such recurrent multi-tetris optimisation by hands many many times in row be very tedious.
I should have no problems with combining every possible sequence of L0 and R1 lists, and L1 and R0, for each hole, once they're made.
And I do not know just how lengthy the process will be when there's that many permutations. But since this method isn't an in-game simulation (isn't bound by advancing frames), I don't think it will take too long. This current one-permutation test takes less than a second.
I'm not sure I fully understand what your one "R+1b" fits into.
Well, since the piece RNG is generally sequential, I'm not if such a major frame difference will be possible.
Do we want to try to brute force the initial stack building at all? That part seems ok to do by hand but theoretically I could also test a list of usable piece orders for it too.
Hmm, I think I'm a bit confused about the start, at least as far as your "L-1" builds go. If we're filling in 5 lines instead of 4 then, do they all require two additional I pieces in the fifth line?
Right branch slightly more complexity.
First option for right branch can be also "I"-piece at bottom. In this case above need to build standart "R+0 subgroup" for hole#10 above it.
Second option for right branch is to use two "J"-pieces at bottom. In this case above it need to build 3x4 square. (I used this option in my test attempt for first knee.)
And at last third option for right branch available only in case if top of Tree has not 3 but 4 flat blocks - is possible to use more exotic builds.