diff --git a/demo2.cpp b/demo2.cpp
index 8f15cf9..91fcfd7 100644
--- a/demo2.cpp
+++ b/demo2.cpp
@@ -22,7 +22,8 @@
 
 //#define RENDER_PRECISE
   /* ^ Turns on rendering using a more precise but slower algorithm. This can
-       be seen at less shaky head bobbing when moving. */
+       be seen at less shaky head bobbing when moving. However the latter
+       algorithm doesn't support rolling doors (these will be turned off). */
 
 //#define NO_TEXTURES
   /* ^ Turns off textures and only uses colors, which increases FPS. */
@@ -767,11 +768,13 @@ unsigned char textureAverageColors[TEXTURES];
 
 Unit floorHeightAt(int16_t x, int16_t y)
 {
-  if (x >= 0 && x < LEVEL_X_RES && y >= 0 && y < LEVEL_Y_RES)
-    return level[(LEVEL_Y_RES - y -1) * LEVEL_X_RES + x] == 0 ?
-      0 : UNITS_PER_SQUARE * 2; 
+  Unit square = level[(LEVEL_Y_RES - y -1) * LEVEL_X_RES + x];
 
-  return UNITS_PER_SQUARE * 2;
+#ifdef RENDER_PRECISE
+  return square == 0 || square == 6 ? 0 : UNITS_PER_SQUARE * 2;
+#else
+  return square == 0 ? 0 : UNITS_PER_SQUARE * 2;
+#endif
 }
 
 Unit collisionAt(int16_t x, int16_t y)