Expanded palette hack

as for Square code, there's a loop that includes two sequences of "ASL / ROR $10" to reverse the bit order in bytes.  what i have now tweaks the ends, saving 3 * 2 = 6  cycles per loop iteration (of 64).

but it just dawned on me: we're reversing two bytes back-to-back, so intersperse the fuckers!

Code:

LDA $03C0,X
STA $10
LDA $10C0,X

; do next 2 instructions 8 times
ROL
ROR $10

ROL
STA $03C0,X
LDA $10
STA $10C0,X

CPU cycles:

asl a = 2
ror d = 5

lda d = 3

---

rol a = 2
sta d = 3

----------

that'll save (7 * 8) - 5 + 3 = 54 cycles per loop iteration (of 64).

EDIT 4: switched back to using Var $10 as opposed to XBA-pair initial method, as it's faster.

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elsewhere and unrelated:

if we bring down C1_3E37 thru C1_3E47 to after the added "REP #$30", we can word-ize the loop.  it'll add 3 instructions taking 4 bytes (and clobber Variable $11, which we're no longer using and was just a scratch variable anyway), but we cut the iterations in half.

inserting an "STA $1A" (or STX?) at C1_3E2B will let us zap 4 instructions of the new code.  we can do something similar with Y and $1C, but we'll need an "STZ $1D", so we're saving 2 bytes and negligible cycles at most.  it's a bit odd to relocate the $1A store but not the $1C, yet if speed is paramount...