diff --git a/th01/main/player/shots.cpp b/th01/main/player/shots.cpp
index b2c2671e..45e50449 100644
--- a/th01/main/player/shots.cpp
+++ b/th01/main/player/shots.cpp
@@ -1,6 +1,7 @@
 #include "th01/snd/mdrv2.h"
 #include "th01/formats/ptn.hpp"
 #include "th01/hardware/egc.h"
+#include "th01/math/overlap.hpp"
 #include "th01/main/playfld.hpp"
 #include "th01/main/player/player.hpp"
 #include "th01/main/player/orb.hpp"
@@ -93,12 +94,10 @@ bool16 CShots::hittest_orb(int i, int orb_left, int orb_top)
 	if(moving[i] == false) {
 		return false;
 	}
-	if(
-		((left[i] - orb_left) < ORB_W)
-		&& ((left[i] - orb_left) > (-SHOT_W))
-		&& ((top[i] - orb_top) < ORB_H)
-		&& ((top[i] - orb_top) > (-SHOT_H))
-	) {
+	if(overlap_lt_gt(
+		left[i], top[i], SHOT_W, SHOT_H,
+		orb_left, orb_top, ORB_W, ORB_H
+	)) {
 		if((left[i] - orb_left) > (SHOT_W / 2)) {
 			orb_velocity_x = OVX_4_LEFT;
 		} else if((left[i] - orb_left) == (SHOT_W / 2)) {
@@ -132,12 +131,15 @@ bool16 CShots::hittest_pellet(int pellet_left, int pellet_top)
 		if(decay_frame[i] == 1) {
 			continue;
 		}
-		if(
-			((left[i] - pellet_left) <= ((SHOT_W / 2) - SHOT_SPRITE_MARGIN))
-			&& ((left[i] - pellet_left) >= -(SHOT_H - SHOT_SPRITE_MARGIN))
-			&& ((top[i] - pellet_top) <= ((SHOT_W / 2) - SHOT_SPRITE_MARGIN))
-			&& ((top[i] - pellet_top) >= -(SHOT_H - SHOT_SPRITE_MARGIN))
-		) {
+		if(overlap_le_ge(
+			left[i], top[i],
+			(SHOT_W - SHOT_SPRITE_MARGIN),
+			(SHOT_H - SHOT_SPRITE_MARGIN),
+			pellet_left,
+			pellet_top,
+			(PELLET_W - SHOT_SPRITE_MARGIN),
+			(PELLET_H - SHOT_SPRITE_MARGIN)
+		)) {
 			on_hit(i);
 			return true;
 		}
@@ -153,12 +155,9 @@ bool16 CShots::hittest_boss(
 		if(moving[i] == false) {
 			continue;
 		}
-		if(
-			(left[i] >= hitbox_left)
-			&& (left[i] <= (hitbox_left + hitbox_w))
-			&& (top[i] >= hitbox_top)
-			&& (top[i] <= (hitbox_top + hitbox_h))
-		) {
+		if(overlap_point_le_ge_wh(
+			left[i], top[i], hitbox_left, hitbox_top, hitbox_w, hitbox_h
+		)) {
 			on_hit(i);
 			return true;
 		}
diff --git a/th01/main/player/shots.hpp b/th01/main/player/shots.hpp
index 7bd7910b..b00063e3 100644
--- a/th01/main/player/shots.hpp
+++ b/th01/main/player/shots.hpp
@@ -1,3 +1,5 @@
+#include "th01/sprites/pellet.h"
+
 static const int SHOT_COUNT = 8;
 
 struct CShots {
diff --git a/th01/math/overlap.hpp b/th01/math/overlap.hpp
new file mode 100644
index 00000000..32ddacb6
--- /dev/null
+++ b/th01/math/overlap.hpp
@@ -0,0 +1,24 @@
+// Generic overlap testing macros for collision detection.
+#define overlap_lt_gt(x1, y1, w1, h1, x2, y2, w2, h2) ( \
+	(((x1) - (x2)) < (w2)) && \
+	(((x1) - (x2)) > -(w1)) && \
+	(((y1) - (y2)) < (h2)) && \
+	(((y1) - (y2)) > -(h1)) \
+)
+
+#define overlap_le_ge(x1, y1, w1, h1, x2, y2, w2, h2) ( \
+	(((x1) - (x2)) <= (w2)) && \
+	(((x1) - (x2)) >= -(w1)) && \
+	(((y1) - (y2)) <= (h2)) && \
+	(((y1) - (y2)) >= -(h1)) \
+)
+
+#define overlap_point_le_ge(x1, y1, left2, top2, right2, bottom2) ( \
+	((x1) >= (left2)) && \
+	((x1) <= (right2)) && \
+	((y1) >= (top2)) && \
+	((y1) <= (bottom2)) \
+)
+
+#define overlap_point_le_ge_wh(x1, y1, left2, top2, w2, h2) \
+	overlap_point_le_ge(x1, y1, left2, top2, (left2 + w2), (top2 + h2))