diff --git a/planar.h b/planar.h
index 4b0487c5..adc6d325 100644
--- a/planar.h
+++ b/planar.h
@@ -52,6 +52,14 @@ typedef enum {
 		const row_dots_t& operator [](pixel_t y) const {
 			return row[y];
 		}
+
+		static pixel_t w() {
+			return (sizeof(row_dots_t) * 8);
+		}
+
+		static pixel_t h() {
+			return H;
+		}
 	};
 
 	#define dot_rect_t(w, h) DotRect<dots_t(w), h>
diff --git a/th01/hardware/grcg8x8m.cpp b/th01/hardware/grcg8x8m.cpp
index 6774c038..b8631825 100644
--- a/th01/hardware/grcg8x8m.cpp
+++ b/th01/hardware/grcg8x8m.cpp
@@ -8,7 +8,7 @@ void grcg_put_8x8_mono(
 )
 {
 	grcg_setcolor_rmw(col);
-	for(pixel_t y = 0; y < 8; y++) {
+	for(pixel_t y = 0; y < sprite.h(); y++) {
 		dots16_t d = (
 			(sprite[y] >> first_bit) + (sprite[y] << (16 - first_bit))
 		);