LogicGameMode::encode reads its return value out of getCheckSum() and
only then writes it:
v15 = ChecksumEncoder::getCheckSum(a2);
(...vptr+88)(a2, v15); // the checkpoint vint
return v15;
we were reading ours after that write, so the closing checkpoint was
folded into the number we compared. the two could never match, whatever
the simulation did - which is why tick 41 disagreed with six untouched
towers on the field.
write() now hands back the value it wrote, the way encode() does.
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