diff --git a/pc98.h b/ReC98.h
similarity index 52%
rename from pc98.h
rename to ReC98.h
index 125dd9fe..f3eec688 100644
--- a/pc98.h
+++ b/ReC98.h
@@ -1,10 +1,37 @@
 /* ReC98
  * -----
- * Some useful PC-98 hardware constants
+ * Some useful random constants and macros
  */
 
-// VRAM planes
-// -----------
+// Macros
+// ------
+#define CLAMP_INC(val, max) \
+	(val)++; \
+	if((val) > (max)) { \
+		(val) = (max); \
+	}
+
+#define CLAMP_DEC(val, min) \
+	(val)--; \
+	if((val) < (min)) { \
+		(val) = (min); \
+	}
+
+#define RING_INC(val, ring_end) \
+	(val)++; \
+	if((val) > (ring_end)) { \
+		(val) = 0; \
+	}
+
+#define RING_DEC(val, ring_end) \
+	(val)--; \
+	if((val) < 0) { \
+		(val) = ring_end; \
+	}
+// ------
+
+// PC-98 VRAM planes
+// -----------------
 typedef enum {
 	PL_B, PL_R, PL_G, PL_E, PL_COUNT
 } vram_plane_t;
@@ -26,4 +53,4 @@ extern char *VRAM_PLANE_E;
 	}
 
 #define VRAM_OFFSET(x, y) ((x) >> 3) + (y << 6) + (y << 4)
-// -----------
+// -----------------
diff --git a/th01/th01.h b/th01/th01.h
index f45183df..fe401866 100644
--- a/th01/th01.h
+++ b/th01/th01.h
@@ -3,7 +3,7 @@
  * Include file for TH01
  */
 
-#include "pc98.h"
+#include "ReC98.h"
 
 // Hardware
 void graph_accesspage_func(int page);
diff --git a/th02/op_05.c b/th02/op_05.c
index c26807e0..d8d21769 100644
--- a/th02/op_05.c
+++ b/th02/op_05.c
@@ -39,22 +39,22 @@ void copy_pic_back(int sel, int highlight)
 	int x, y;
 	if(!highlight) {
 		switch(sel) {
-			case 0:	x =  16; y = 128; break;
-			case 1:	x = 224; y = 224; break;
+			case 0: x =  16; y = 128; break;
+			case 1: x = 224; y = 224; break;
 			case 2: x = 432; y = 128; break;
 		}
 		graph_copy_region_from_1_to_0(x, y, 16, 144);
 		graph_copy_region_from_1_to_0(x, y, 192, 10);
 	} else {
 		switch(sel) {
-			case 0:	x = 208; y = 136; break;
-			case 1:	x = 416; y = 232; break;
+			case 0: x = 208; y = 136; break;
+			case 1: x = 416; y = 232; break;
 			case 2: x = 624; y = 136; break;
 		}
 		graph_copy_region_from_1_to_0(x, y, 16, 144);
 		switch(sel) {
-			case 0:	x =  24; y = 272; break;
-			case 1:	x = 232; y = 368; break;
+			case 0: x =  24; y = 272; break;
+			case 1: x = 232; y = 368; break;
 			case 2: x = 440; y = 272; break;
 		}
 		graph_copy_region_from_1_to_0(x, y, 192, 8);
@@ -81,8 +81,8 @@ void draw_shottype_desc(int sel, int color)
 {
 	int x, y;
 	switch(sel) {
-		case 0:	x =  16; y = 296; break;
-		case 1:	x = 224; y = 136; break;
+		case 0: x =  16; y = 296; break;
+		case 1: x = 224; y = 136; break;
 		case 2: x = 432; y = 296; break;
 	}
 	grcg_setcolor(GC_RMW, color);
@@ -176,10 +176,7 @@ void pascal shottype_menu(void)
 				frame_delay(1);
 				darken_pic_at(pic_x[sel] + 8, pic_y[sel] + 8);
 
-				sel--;
-				if(sel < 0) {
-					sel = SHOTTYPE_COUNT - 1;
-				}
+				RING_DEC(sel, SHOTTYPE_COUNT - 1);
 				DRAW_NEW_SEL();
 			}
 			if(input & INPUT_RIGHT) {
@@ -191,10 +188,7 @@ void pascal shottype_menu(void)
 				frame_delay(1);
 				darken_pic_at(pic_x[sel] + 8, pic_y[sel] + 8);
 
-				sel++;
-				if(sel > SHOTTYPE_COUNT - 1) {
-					sel = 0;
-				}
+				RING_INC(sel, SHOTTYPE_COUNT - 1);
 				DRAW_NEW_SEL();
 			}
 			if(input & INPUT_SHOT || input & INPUT_OK) {
diff --git a/th02/th02.h b/th02/th02.h
index 5fb0d116..6f45707f 100644
--- a/th02/th02.h
+++ b/th02/th02.h
@@ -3,7 +3,7 @@
  * Include file for TH02
  */
 
-#include "pc98.h"
+#include "ReC98.h"
 
 // Formats
 #define PI_SLOTS 6