Invariants and monovariants

An invariant is a quantity that no allowed move ever changes; a monovariant only ever moves one way. Finding one turns an endless search into a one-line argument about what states can ever be reached, or about why a process has to stop.

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Work through it

LearnWhat it is, how to spot it, a worked example, and where it goes wrong.
Practice — 3-point ladderNo problems written at this tier yet.Nothing written at this tier yet
Practice — 4-point ladderNo problems written at this tier yet.Nothing written at this tier yet
Practice — 5-point ladder4 problems. Three in a row finishes it.0/3 in a row · 0/4 solved
Skill quizFinish every ladder that has problems first.Finish the ladders above first

Before and after

Needs first

LOG-05Parity arguments

Opens up

Nothing yet. No other skill in the Atlas lists this one as a prerequisite.

In official papers

No indexed official paper question has been tagged with LOG-06 yet. The index grows one paper at a time, and it records only question numbers, point values and our own skill tags — never the problems themselves.

See the papers indexed so far

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