diff --git a/src/editor/level_editor.jai b/src/editor/level_editor.jai
index a73f563..4c75e0f 100644
--- a/src/editor/level_editor.jai
+++ b/src/editor/level_editor.jai
@@ -498,10 +498,9 @@ add_trile :: (name: string, x: s32, y: s32, z: s32, orientation: u8 = 0) {
 		array_add(*chunk.groups, group);
 	}
 	invalidate_buried_around(*curworld.world, x, y, z);
-    trile, ok := get_trile(name);
+	trile, ok := get_trile(name);
 	if !ok || trile.skip_collision then return;
-    new_state : Occupancy_State = ifx trile.is_stairs then .OCCUPIED_STAIRS else .OCCUPIED;
-	chunk_set_occupancy_mask_at(chunk, lx, ly, lz, new_state);
+	chunk_set_occupancy_mask_at(chunk, lx, ly, lz, occupancy_state_for(trile, orientation));
 } @Command
 
 remove_trile :: (x: s32, y: s32, z: s32) {
diff --git a/src/world.jai b/src/world.jai
index ddf5b02..d65988e 100644
--- a/src/world.jai
+++ b/src/world.jai
@@ -144,16 +144,21 @@ World :: struct {
     rdm_lookup        : [..]Rdm_Atlas_Entry;   // populated by bake (Step 5) and by loader (Step 6)
 }
 
+// The mask state a colliding trile instance contributes. Stairs only count as
+// stairs when upright.
+occupancy_state_for :: inline (trile: *Trile, orientation: u8) -> Occupancy_State {
+    if trile.is_stairs && orientation < 4  return .OCCUPIED_STAIRS;
+    return .OCCUPIED;
+}
+
 calculate_and_set_chunk_occupancy_mask :: (chunk: *Chunk) {
     chunk_clear_full_occupancy_mask(chunk);
     
     for group: chunk.groups {
         trile, ok := get_trile(group.trile_name);
         if !ok || trile.skip_collision then continue;
-        new_state : Occupancy_State = ifx trile.is_stairs then .OCCUPIED_STAIRS else .OCCUPIED;
-        
         for instance : group.instances {
-            chunk_set_occupancy_mask_at(chunk, instance.x, instance.y, instance.z, new_state);
+            chunk_set_occupancy_mask_at(chunk, instance.x, instance.y, instance.z, occupancy_state_for(trile, instance.orientation));
         }
     }
 }
@@ -436,6 +441,22 @@ get_note_locations :: (note : string) -> []Vector3 {
     return result;
 }
 
+trile_instance_at_chunk :: (chunk: *Chunk, lx: s32, ly: s32, lz: s32) -> (bool, Trile_Instance, *Trile) {
+    for group : chunk.groups {
+        for instance : group.instances {
+            if instance.x == lx && instance.y == ly && instance.z == lz {
+                trile, ok := get_trile(group.trile_name);
+                if !ok {
+                    print("Error: did not find matching trile for group %\n", group.trile_name);
+                    return false, .{}, null;
+                }
+                return true, instance, trile;
+            }
+        }
+    }
+    return false, .{}, null;
+}
+
 invalidate_buried_around :: (world: *World, wx: s32, wy: s32, wz: s32) {
     recompute_buried_at_cell(world, wx, wy, wz);
     for axis: 0..5 {