diff --git a/src/chaos-drop.h b/src/chaos-drop.h
index b211cc4..cf633f7 100644
--- a/src/chaos-drop.h
+++ b/src/chaos-drop.h
@@ -155,6 +155,9 @@ struct game {
    struct element_mirror *mirror;
    struct element_plane *plane;
    struct element_text *text;
+   /* A dynamic plane y value; mostly redundant from plane->y, used to optimize
+      away some checks during collisions with the plane */
+   num plane_collision[2];
 
    /* Distance traversed within the current level */
    num depth;
diff --git a/src/main.cc b/src/main.cc
index ef8cdd2..871cc47 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -459,6 +459,19 @@ int game_update(struct game *g, bool *debug)
         game_next_level_or_menu(g);
     }
 
+    // Pre-compute plane collision info
+
+    num pc = g->plane ? g->plane->y - g->depth : num(0x7fff);
+
+    if(g->plane->type == ELEMENT_PLANE_INVIS) {
+        g->plane_collision[0] = num(0x7fff);
+        g->plane_collision[1] = pc;
+    }
+    else {
+        g->plane_collision[0] = pc;
+        g->plane_collision[1] = pc;
+    }
+
     return 0;
 }
 
@@ -504,6 +517,8 @@ int main(void)
     g.blank_frames = 0;
     g.neon_position = 0;
     g.neon_period = 64;
+    g.plane_collision[0] = num(0x7fff);
+    g.plane_collision[1] = num(0x7fff);
     game_load_menu(&g);
     game = &g;
 
diff --git a/src/raytracing.cc b/src/raytracing.cc
index b547c3b..e686297 100644
--- a/src/raytracing.cc
+++ b/src/raytracing.cc
@@ -79,16 +79,16 @@ static int cast_ray(struct game const *g, svec3 const &origin,
 
     if(hitz && (!hitx || (tz_rx_rz < tx_rx_rz) ^ rx_rz_sign)) {
         if(hitz == TOP)
-            *t = num16::div_positive(num16(WORLD_SIZE) - origin.z, rayDir.z);
+            *t = (num16(WORLD_SIZE) - origin.z) / rayDir.z;
         else
-            *t = num16::div_positive(origin.z + num16(WORLD_SIZE), -rayDir.z);
+            *t = (origin.z + num16(WORLD_SIZE)) / -rayDir.z;
         hit = hitz;
     }
     else if(__builtin_expect(hitx, 1)) {
         if(hitx == RIGHT)
-            *t = num16::div_positive(num16(WORLD_SIZE) - origin.x, rayDir.x);
+            *t = (num16(WORLD_SIZE) - origin.x) / rayDir.x;
         else
-            *t = num16::div_positive(origin.x + num16(WORLD_SIZE), -rayDir.x);
+            *t = (origin.x + num16(WORLD_SIZE)) / -rayDir.x;
         hit = hitx;
     }
 
@@ -101,19 +101,16 @@ static int cast_ray(struct game const *g, svec3 const &origin,
 
     /* Determine if there is an intersection with the object plane */
 
-    if(__builtin_expect(
-        g->plane
-        && (*collision_y > g->plane->y - g->depth)
-        && (g->plane->type != ELEMENT_PLANE_INVIS || secondary),
-    0)) {
-        num16 plane_y = num16(g->plane->y - g->depth);
+    num pc = g->plane_collision[secondary];
+    if(__builtin_expect(*collision_y > pc, 0)) {
+        num16 plane_y = num16(pc);
         num16 plane_t = (plane_y - origin.y) / rayDir.y;
         num16 plane_x = origin.x + plane_t * rayDir.x;
         num16 plane_z = origin.z + plane_t * rayDir.z;
 
         if(level_plane_collides(plane_x, plane_z, g->plane->shape)) {
             *t = plane_t;
-            *collision_y = g->plane->y - g->depth;
+            *collision_y = pc;
             return OBJECT_PLANE;
         }
     }