Drift

Drift

Shepherd an allele through bottlenecks, founder events and selection without letting Wright–Fisher sampling fix it or lose it.

A population, one allele at a stated frequency, and a horizon of events you can read ahead: dry summers, a founding party, seasons when birds favour one morph. Each generation, pull at most one lever from a small budget — a refuge that keeps more individuals breeding, a corridor to a neighbouring population, relief from selection — then advance and let the seeded sampler draw the next gene pool. Small populations wander; the levers change how far.

• 1One Small MeadowMore at once
• 2A Corridor Through the HedgeMore at once
• 3Birds on Clean BarkAdversityMore at onceSelection is added to drift here, which reads only once drift alone has been seen to move a frequency in the meadow and the island.
• 4The Pale-Leaf AlleleAdversity
• 5Too Few to SaveAdversityA designed failure: it teaches only after the earlier levels have shown the levers working, so their failing here is the finding.

The tag on each level says how it gets harder. Levels gate on ideas, not on each other — jump wherever it gets interesting.