Ticking the sim clock lived on Game, so game.is_changed() stayed true and restyle_3d / render_map / the sidebar rebuilt at 60 Hz. Move the timer to SimClock, only dirty Game on real steps or attendance flips, cache owned/selected tiles, and walk the heard set for noise stipple. Defense: wiki/interface/material-render.md perf debt 5 / criterion 6 — wall-clock pacing must not force full material restyle every frame.