diff --git a/mapserver/src/config.rs b/mapserver/src/config.rs
index 245a7b2..ee8b12a 100644
--- a/mapserver/src/config.rs
+++ b/mapserver/src/config.rs
@@ -25,7 +25,6 @@ impl Default for Config {
 			mapper_threads: 4,
 			minetestmapper_args: vec![
 				String::from("--drawalpha"),
-				String::from("--noemptyimage"),
 				String::from("--max-y"),
 				String::from("2000"),
 				String::from("--colors"),
diff --git a/mapserver/src/main.rs b/mapserver/src/main.rs
index 193be2a..0aa6160 100644
--- a/mapserver/src/main.rs
+++ b/mapserver/src/main.rs
@@ -10,6 +10,7 @@ use tide::Request;
 
 #[derive(Debug)]
 enum Error {
+	Image(image::ImageError),
 	Io(std::io::Error),
 	Minetestmapper,
 	Todo,
@@ -114,10 +115,56 @@ fn generate_tile(
 				drop(tasks_guard);
 
 				let res: Result<(), Error> = try {
-					if z == config.zoom_default {
-						run_minetestmapper(z, x, y, tile_dir, tile_path, config)?;
-					} else {
-						Err(Error::Todo)?;
+					match z.cmp(&config.zoom_default) {
+						std::cmp::Ordering::Equal => {
+							run_minetestmapper(z, x, y, tile_dir, tile_path, config)?
+						}
+						std::cmp::Ordering::Less => {
+							let tile1_path =
+								get_dep_tile(z + 1, x * 2, y * 2, tasks.clone(), config.clone())?;
+							let tile2_path = get_dep_tile(
+								z + 1,
+								x * 2,
+								y * 2 + 1,
+								tasks.clone(),
+								config.clone(),
+							)?;
+							let tile3_path = get_dep_tile(
+								z + 1,
+								x * 2 + 1,
+								y * 2,
+								tasks.clone(),
+								config.clone(),
+							)?;
+							let tile4_path = get_dep_tile(
+								z + 1,
+								x * 2 + 1,
+								y * 2 + 1,
+								tasks.clone(),
+								config.clone(),
+							)?;
+
+							let tile1 = image::open(tile1_path).map_err(Error::Image)?.into_rgb8();
+							let tile2 = image::open(tile2_path).map_err(Error::Image)?.into_rgb8();
+							let tile3 = image::open(tile3_path).map_err(Error::Image)?.into_rgb8();
+							let tile4 = image::open(tile4_path).map_err(Error::Image)?.into_rgb8();
+
+							let mut tile = image::ImageBuffer::<image::Rgb<u8>, Vec<u8>>::new(
+								config.tile_size as u32 * 2,
+								config.tile_size as u32 * 2,
+							);
+							image::imageops::replace(&mut tile, &tile1, 0, 0);
+							image::imageops::replace(&mut tile, &tile2, 0, config.tile_size as i64);
+							image::imageops::replace(&mut tile, &tile3, config.tile_size as i64, 0);
+							image::imageops::replace(
+								&mut tile,
+								&tile4,
+								config.tile_size as i64,
+								config.tile_size as i64,
+							);
+							tile.save(tile_path).map_err(Error::Image)?;
+						}
+						std::cmp::Ordering::Greater => Err(Error::Todo)?,
 					}
 				};
 
@@ -132,6 +179,44 @@ fn generate_tile(
 	}
 }
 
+fn get_dep_tile(
+	z: i32,
+	x: i32,
+	y: i32,
+	tasks: Arc<RwLock<HashMap<(i32, i32, i32), Sender<()>>>>,
+	config: Arc<config::Config>,
+) -> Result<String, Error> {
+	let tile_dir = format!("{}{}/{}", config.output_path, z, x);
+	let tile_path = format!("{}/{}.png", tile_dir, y);
+
+	match std::fs::metadata(&tile_path) {
+		Ok(metadata) => match metadata.modified() {
+			Ok(modified_time) => {
+				if SystemTime::now()
+					.duration_since(modified_time)
+					.unwrap()
+					.as_secs() > config.cache_age
+				{
+					generate_tile(z, x, y, &tile_dir, &tile_path, tasks, config)?;
+				}
+			}
+			Err(e) => {
+				warn!("Cannot get modified time of `{}`: {}", tile_path, e);
+				generate_tile(z, x, y, &tile_dir, &tile_path, tasks, config)?;
+			}
+		},
+		Err(e) => {
+			if e.kind() == std::io::ErrorKind::NotFound {
+				debug!("Tile not found `{}`", tile_path);
+			} else {
+				warn!("Cannot get metadata of `{}`: {}", tile_path, e);
+			}
+			generate_tile(z, x, y, &tile_dir, &tile_path, tasks, config)?;
+		}
+	}
+	Ok(tile_path)
+}
+
 fn resp_tile(
 	z: i32,
 	x: i32,
@@ -151,6 +236,11 @@ async fn req_tile(
 	config: Arc<config::Config>,
 ) -> tide::Result {
 	let z: i32 = req.param("z")?.parse()?;
+
+	if z > config.zoom_max || z < config.zoom_min {
+		return Ok(tide::StatusCode::Forbidden.into());
+	}
+
 	let x: i32 = req.param("x")?.parse()?;
 	let y = req.param("y")?;
 	let y = y.strip_suffix(".png").unwrap_or(y).parse()?;