diff --git a/game/grid.go b/game/grid.go
index ffbafee..d59e7ea 100644
--- a/game/grid.go
+++ b/game/grid.go
@@ -40,6 +40,14 @@ func (g *Grid) IsRowFull(y byte) bool {
 	return true
 }
 
+func (g *Grid) MoveRowDown(y, num_rows byte) {
+	w := uint16(g.Width())
+	src := uint16(y) * w
+	dst := uint16(y+num_rows) * w
+	copy(g[dst:dst+w], g[src:src+w])
+	clear(g[src : src+w])
+}
+
 func (g *Grid) ClearRow(y byte) {
 	w := uint16(g.Width())
 	n := uint16(y) * w