Still Alive

Complete Course 4 (Excursion Funnels) without either you or your partner dying, once, the whole course. Deaths are cheap in co-op normally, so the only real trick is patience: take every chamber slowly and don't take risks near goo, lasers or pits. A single death by either player and you start the course over. Do it on the same careful run as Party of Three and Obstacle Building. A cheeky nod to the Portal 1 song.