feat: detect game over condition and switch state.

game/state/handlers/gameplay.go

@@ -110,6 +110,10 @@ func (gp *GamePlay) Update(fsm state.Transitioner, delta float32) {
 				gp.score.Lines(num_rows)
 			}
 			gp.SpawnShape()
+
+			if game.CheckShapeCollision(gp.shape_pos, &gp.shape, &gp.grid) {
+				fsm.Switch("gameover")
+			}
 		} else {
 			gp.shape_pos = new_pos
 		}