Interactive Punnett square builder with four cross types: monohybrid (3:1), dihybrid (9:3:3:1), testcross (1:1), and incomplete dominance. Select parent genotypes via dropdowns to regenerate the square and ratio donut chart instantly. Simulate 100 offspring to compare empirical vs expected ratios. Color-coded cells distinguish dominant, heterozygous, and recessive genotypes.