diff --git a/assets.h b/assets.h
index 2dde124..cca55f2 100644
--- a/assets.h
+++ b/assets.h
@@ -24,6 +24,8 @@ static const char *LCR_maps[] =
   "#=s0B0 #fd910" // concrete wall
   "#^s1A0 #fk110" // ramps before wall
 
+  "#nu0j1 #ly0j1 #AA0j1 "
+
   "#vw0m0"
   "#vx0m0J"
   "#vw0l0L"
diff --git a/map.h b/map.h
index 34b46c3..ca62e97 100644
--- a/map.h
+++ b/map.h
@@ -96,7 +96,6 @@
 #define LCR_BLOCK_RAMP_12           '<'  ///< plain ramp, 1/2 size
 #define LCR_BLOCK_RAMP_14           '_'  ///< plain ramp, 1/4 size
 #define LCR_BLOCK_RAMP_CORNER       'v'  ///< corner of ramp
-
 #define LCR_BLOCK_RAMP_CURVED_PLAT  ']'  ///< curved ramp with top platgform
 #define LCR_BLOCK_RAMP_CURVED       ')'  ///< curv. ramp without top platf.
 #define LCR_BLOCK_RAMP_CURVED_WALL  '}'  ///< curved ramp plus small wall
@@ -108,6 +107,11 @@
 #define LCR_BLOCK_FULL_FAN          'o'
 #define LCR_BLOCK_BUMP              '~'  ///< small bump on the road
 
+#define LCR_BLOCK_CORNER_CONVEX     'n'
+#define LCR_BLOCK_CORNER_CONCAVE    'l'
+
+
+
 #define LCR_BLOCK_CHECKPOINT_0      '+'  ///< checkpoint, not taken
 #define LCR_BLOCK_CHECKPOINT_1      '\'' ///< checkpoint, taken
 
@@ -821,6 +825,28 @@ void LCR_mapGetBlockShape(uint8_t blockType, uint8_t transform,
       break;
     }
 
+case LCR_BLOCK_CORNER_CONVEX:
+case LCR_BLOCK_CORNER_CONCAVE:
+{
+  uint8_t
+    mx = blockType == LCR_BLOCK_CORNER_CONVEX ? 4 : 2,
+    mz = blockType == LCR_BLOCK_CORNER_CONVEX ? 2 : 4;
+
+  ADD(0,0,0)     ADD(0,4,6)     ADD(0,0,6)       // left
+  ADD(0,0,0)     ADD(0,4,0)     ADD(0,4,6)       // left
+  ADD(6,0,6)     ADD(0,0,6)     ADD(0,4,6)       // back
+  ADD(0,4,6)     ADD(6,4,6)     ADD(6,0,6)       // back
+  ADD(0,0,0)     ADD(mx,4,mz)   ADD(0,4,0)       // right
+  ADD(mx,0,mz)   ADD(mx,4,mz)   ADD(0,0,0)
+  ADD(6,4,6)     ADD(mx,4,mz)   ADD(6,0,6)
+  ADD(6,0,6)     ADD(mx,4,mz)   ADD(mx,0,mz)
+  ADD(0,4,0)     ADD(mx,4,mz)   ADD(0,4,6)       // top
+  ADD(0,4,6)     ADD(mx,4,mz)   ADD(6,4,6)
+  ADD(0,0,0)     ADD(0,0,6)     ADD(mx,0,mz)     // bottom
+  ADD(0,0,6)     ADD(6,0,6)     ADD(mx,0,mz)
+  break;
+}
+
     case LCR_BLOCK_BUMP:
       ADD(3,0,0)     ADD(6,0,3)     ADD(3,1,3)       // top
       ADD(6,0,3)     ADD(3,0,6)     ADD(3,1,3)
diff --git a/racing.h b/racing.h
index ecf8044..5126612 100644
--- a/racing.h
+++ b/racing.h
@@ -205,6 +205,40 @@ TPE_Vec3 _LCR_racingBlockEnvFunc(TPE_Vec3 point, const uint8_t *block)
       break;
     }
 
+    case LCR_BLOCK_CORNER_CONVEX:
+    case LCR_BLOCK_CORNER_CONCAVE:
+    {
+      TPE_Unit sides[6];
+      sides[0] = -1 * LCR_PHYSICS_UNIT / 2;
+      sides[1] = LCR_PHYSICS_UNIT / 2;
+      sides[2] = -1 * LCR_PHYSICS_UNIT / 2;
+      sides[3] = -1 * LCR_PHYSICS_UNIT / 2;
+      sides[4] = LCR_PHYSICS_UNIT / 5;
+      sides[5] = -1 * LCR_PHYSICS_UNIT / 5;
+
+      if (block[0] == LCR_BLOCK_CORNER_CONCAVE)
+      {
+        sides[4] *= -1;
+        sides[5] *= -1; 
+      }
+
+      _CHECK_NEXT(TPE_envAATriPrism(point,TPE_vec3(0,0,0),sides,LCR_PHYSICS_UNIT / 2
+        ,1));
+
+      sides[2] = sides[4];
+      sides[3] = sides[5];
+
+      sides[4] = LCR_PHYSICS_UNIT / 2;
+      sides[5] = LCR_PHYSICS_UNIT / 2;
+
+      _CHECK_NEXT(TPE_envAATriPrism(point,TPE_vec3(0,0,0),sides,LCR_PHYSICS_UNIT / 2
+        ,1));
+
+      point = vBest;
+
+      break;
+    }
+
 #undef _CHECK_NEXT
 
     case LCR_BLOCK_RAMP_CORNER:
@@ -434,8 +468,6 @@ TPE_Vec3 _LCR_racingEnvironmentFunction(TPE_Vec3 point, TPE_Unit maxDist)
   TPE_ENV_END
 }
 
-
-
 LCR_GameUnit LCR_racingGetCarSpeedUnsigned(void)
 {
   return LCR_racing.carSpeed >= 0 ? LCR_racing.carSpeed :
diff --git a/renderer.h b/renderer.h
index 1bdd91e..45acc3e 100644
--- a/renderer.h
+++ b/renderer.h
@@ -720,11 +720,25 @@ uint8_t _LCR_buildMapModel(void)
             uint8_t blockMat = LCR_mapBlockGetMaterial(block);
 
 #define VERT(n,c) LCR_renderer.mapVerts[3 * n + c]
+
             triData =
-              (((VERT(triIndices[0],0) == VERT(triIndices[1],0)) &&
+              (((VERT(triIndices[0],0) == VERT(triIndices[1],0)) && // same X?
               (VERT(triIndices[1],0) == VERT(triIndices[2],0))) << 4) |
-              (((VERT(triIndices[0],2) == VERT(triIndices[1],2)) &&
+              (((VERT(triIndices[0],2) == VERT(triIndices[1],2)) && // same Z?
               (VERT(triIndices[1],2) == VERT(triIndices[2],2))) << 5);
+
+            if (!(triData & 0xf0))
+            {
+              // diagonal walls
+
+              triData = (
+                (VERT(triIndices[0],0) == VERT(triIndices[1],0) &&
+                VERT(triIndices[0],2) == VERT(triIndices[1],2)) |
+                (VERT(triIndices[1],0) == VERT(triIndices[2],0) &&
+                VERT(triIndices[1],2) == VERT(triIndices[2],2)) |
+                (VERT(triIndices[0],0) == VERT(triIndices[2],0) &&
+                VERT(triIndices[0],2) == VERT(triIndices[2],2))) << 4;
+            }
 #undef VERT
 
             if (triData & 0xf0) // wall?