Puzzle Description:

This puzzle is courtesy of my son. It depicts his sister's beloved unicorn toy which he calls a demon just to tease her. Siblings, am I right?

#1: Web Paint-By-Number Robot (webpbn) on Jan 2, 2023

Unpublished by rebbers

Republished without change by rebbers

Nice, tricky solve! I think I got it with moderate lookahead, but maybe some of this is deep:
LL (96%)
EL on R39: R39C12-14,C27-28 are white
LL
EL on R29 (look at R31): R29C12-13 is white
LL
EL on C18 (look at C15): C18R34-37 is white
LL
EL on left 3 in R29 (look at R32): R29C14 is white
LL
EL on C26 (look at C25 AND C27): C26R33-34 is white
LL
EL/2-way on C14 (look at C12 AND C13): C14R33 is white
LL
EL on C13 (look at C12): C13R32 is white
LL
EL on 2 in C25 (look at C26 AND C27): C25R38-39 is black
LL
EL on C15 (look at C16): C15R34-35 is white
3-way on C15 (R29-30, R32-33, or R37 is black):
either C15R30 is black then R33C18 is black
or C15R33 is black
or C15R37 is black then R33C13 is black
So R33 is white except for C13,C15,C18.
LL to finish

I agree with Philip's first 2 steps (EL on R39 and R29) but for the 3rd I'm not sure how R34-35 get eliminated doing EL on C18. (I do, however, see how R36-37 are eliminated.)

Picking up from there:

R29: Regardless of whether the 2nd 3 goes into C25 or C28, R30-31 C25 are black. LL.

R29: However the first 3 is finished, R31 C17-18 are black. LL.

C18: However the 3 is finished, R29-30 C17 are black. LL.

C14: If R33 is black, C12 is made invalid, so this square is white. LL.

C26: if the 3 goes into R33-34, R37C27 will need to be black, which places the 2 in C25 into R38-39. This makes C26 invalid, so R33-34 C26 are white. LL.

C13: Whether the 4 goes into R34 or into R38, R34C12 will be white.

C13: If the 4 goes into R32, either R36 or R38 will need to put an additional black into C13, making the column invalid. Therefore R32C18 is white. Minimal LL.

R36: If the 2nd 2 is placed in C15-16, it will make C13 invalid in 2 moves, so these squares are white.

R36: However the 2nd 2 is placed, it will complete R35. R35 C15-16, C26, and C28 are white. LL.

C18: If the 3 goes into R33, it makes C16 invalid in 2 moves, therefore R33C18 is white. LL.

C15: If the 2 is placed within R32-34, it makes C16 invalid, so these squares are white.

LL to finish.

Found to be solvable with moderate lookahead by wombatilim.

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