diff --git a/server/src/blocks.rs b/server/src/blocks.rs
index 28b477e..44a188e 100644
--- a/server/src/blocks.rs
+++ b/server/src/blocks.rs
@@ -5,7 +5,7 @@ use anyhow::{Ok, anyhow};
 use nalgebra::Vector3;
 use rstar::{PointDistance, RTree, RTreeObject, AABB, Envelope};
 use serde::{Deserialize, Serialize};
-use tokio::sync::{RwLock, OwnedRwLockReadGuard};
+use tokio::sync::{RwLock, OwnedRwLockReadGuard, OwnedRwLockWriteGuard};
 
 use crate::{turtle::TurtleCommand, paths::{self, TRANSPARENT}};
 
@@ -98,6 +98,10 @@ impl SharedWorld {
     pub async fn lock(self) -> OwnedRwLockReadGuard<World> {
         self.state.read_owned().await
     }
+
+    pub async fn lock_mut(self) -> OwnedRwLockWriteGuard<World> {
+        self.state.write_owned().await
+    }
 }
 
 #[derive(Serialize, Deserialize, Clone, Debug)]
diff --git a/server/src/construct.rs b/server/src/construct.rs
index 830d9ef..e7588b1 100644
--- a/server/src/construct.rs
+++ b/server/src/construct.rs
@@ -13,24 +13,20 @@ fn schematic2world(region: &Schematic) -> anyhow::Result<World> {
     let mut world = World::new();
 
     let min = region.origin().context("bad schematic")?;
-    let area = Vec3::new(
-        region.width() as i32,
-        region.height() as i32,
-        region.length() as i32,
-    );
-    info!("area {}", area);
 
     for (position, block) in region.blocks() {
-        println!("{:#?}, {}", block, position);
 
         let name = match block {
                 BlockState::AIR => None,
+                BlockState(20) => None, // Glass
+                BlockState(102) => None, // Glass pane
+                BlockState(95) => None, // Stained glass
+                BlockState(160) => None, // Stained glass pane
                 // who cares
                 _ => Some("terrestria:hemlock_planks")
             }.map(|s| s.to_string());
 
         if let Some(name) = name {
-            println!("{:#?}, {:?}", name, block);
             let block = Block {
                 name,
                 pos: position - min,
@@ -98,6 +94,15 @@ impl BuildSimple {
     async fn build_layer(&self, turtle: TurtleCommander, layer: i32) -> Option<()> {
         let layer_size = Vec3::new(self.size.x, 1, self.size.z);
 
+        // assume the layer is empty for better pathfinding
+        let mut world = turtle.world().lock_mut().await;
+        for point in (0..layer_size.product()).map(|n| fill(layer_size, n)) {
+            if let None = world.get(point) {
+                world.set(Block { name: "minecraft:air".into(), pos: point })
+            }
+        }
+        drop(world);
+
         for point in (0..layer_size.product())
             .map(|n| fill(layer_size, n)) {
             let point = point + Vec3::y() * layer;
diff --git a/server/src/turtle_api.rs b/server/src/turtle_api.rs
index 41a598b..7724771 100644
--- a/server/src/turtle_api.rs
+++ b/server/src/turtle_api.rs
@@ -296,7 +296,7 @@ pub(crate) async fn build(
 ) -> &'static str {
     let state = state.read().await;
     let mut schedule = state.tasks.lock().await;
-    let schematic = Schematic::load(&mut fs::File::open("thethinkman.schematic").await.unwrap().into_std().await).unwrap();
+    let schematic = Schematic::load(&mut fs::File::open("schematics/greek-athelete1.schematic").await.unwrap().into_std().await).unwrap();
 
     let input = Position::new(
         Vec3::new(53,73,77),