Hardy-Weinberg assumes no selection. Turn selection on and watch the allele frequency p (of allele A) drift away from equilibrium, generation by generation.
—— allele frequency p of A
□ generation 0 (dashed) solid = final generation
Try: set s = 0 — the line stays flat (Hardy-Weinberg). Now raise s under Stabilizing from a start of p = 0.30 and watch p climb toward 0.5: heterozygote advantage keeps BOTH alleles, the opposite of fixation.