(cond ((collide-grids tetramine grid x y) (setq game-over t)))
(setq next (random-tetramine)))
(t (incf y) (start-timer timer)))))
(cond ((collide-grids tetramine grid x y) (setq game-over t)))
(setq next (random-tetramine)))
(t (incf y) (start-timer timer)))))