· HTML5Saturn: rings that can't hold your weight
Moving platforms were the engine's last big feature, and I didn't want the usual ones. The extra rule: while you stand on a ring it sinks, 18 pixels per second, and only recovers when you step off. When it's about to give, the edge flashes red. Rings become transport, not real estate: hesitate and you sink. The world's third level has my favorite detail: a robot calmly patrols an island whose center is a fake floor. It walks it safely, because the floor only betrays you.