This simulation demonstrates how different voting systems affect election results by counting the exact same 900-voter electorate two ways at once. A spatial model gives each of four fictional parties a geographic stronghold; you control how polarized (regionally clustered) support is and how many districts split the map. The left semicircle fills in live from First-Past-the-Post district winners while the right one fills from D'Hondt proportional allocation of the identical national vote totals — with wasted-vote share and the Gallagher disproportionality index quantifying exactly how far each system drifts from "seats matching votes," the core trade-off behind every real electoral reform debate.