diff --git a/Cargo.lock b/Cargo.lock
index 924f079..bcf7b32 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -17,6 +17,18 @@ version = "2.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "512761e0bb2578dd7380c6baaa0f4ce03e84f95e960231d1dec8bf4d7d6e2627"
 
+[[package]]
+name = "ahash"
+version = "0.8.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e89da841a80418a9b391ebaea17f5c112ffaaa96f621d2c285b5174da76b9011"
+dependencies = [
+ "cfg-if",
+ "once_cell",
+ "version_check",
+ "zerocopy",
+]
+
 [[package]]
 name = "aho-corasick"
 version = "1.1.3"
@@ -26,6 +38,12 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "allocator-api2"
+version = "0.2.21"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "683d7910e743518b0e34f1186f92494becacb047c7b6bf616c96772180fef923"
+
 [[package]]
 name = "android-tzdata"
 version = "0.1.1"
@@ -245,6 +263,12 @@ version = "0.7.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f46ad14479a25103f283c0f10005961cf086d8dc42205bb44c46ac563475dca6"
 
+[[package]]
+name = "codemap"
+version = "0.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b9e769b5c8c8283982a987c6e948e540254f1058d5a74b8794914d4ef5fc2a24"
+
 [[package]]
 name = "colorchoice"
 version = "1.0.3"
@@ -561,8 +585,10 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "c4567c8db10ae91089c99af84c68c38da3ec2f087c3f82960bcdbf3656b6f4d7"
 dependencies = [
  "cfg-if",
+ "js-sys",
  "libc",
  "wasi",
+ "wasm-bindgen",
 ]
 
 [[package]]
@@ -595,11 +621,38 @@ dependencies = [
  "walkdir",
 ]
 
+[[package]]
+name = "grass"
+version = "0.13.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f7a68216437ef68f0738e48d6c7bb9e6e6a92237e001b03d838314b068f33c94"
+dependencies = [
+ "getrandom",
+ "grass_compiler",
+]
+
+[[package]]
+name = "grass_compiler"
+version = "0.13.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2d9e3df7f0222ce5184154973d247c591d9aadc28ce7a73c6cd31100c9facff6"
+dependencies = [
+ "codemap",
+ "indexmap",
+ "lasso",
+ "once_cell",
+ "phf",
+]
+
 [[package]]
 name = "hashbrown"
 version = "0.14.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e5274423e17b7c9fc20b6e7e208532f9b19825d82dfd615708b70edd83df41f1"
+dependencies = [
+ "ahash",
+ "allocator-api2",
+]
 
 [[package]]
 name = "html5ever"
@@ -889,6 +942,15 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "lasso"
+version = "0.7.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6e14eda50a3494b3bf7b9ce51c52434a761e383d7238ce1dd5dcec2fbc13e9fb"
+dependencies = [
+ "hashbrown",
+]
+
 [[package]]
 name = "lazy_static"
 version = "1.5.0"
@@ -1156,6 +1218,7 @@ version = "0.11.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ade2d8b8f33c7333b51bcf0428d37e217e9f32192ae4772156f65063b8ce03dc"
 dependencies = [
+ "phf_macros",
  "phf_shared 0.11.2",
 ]
 
@@ -1189,6 +1252,19 @@ dependencies = [
  "rand",
 ]
 
+[[package]]
+name = "phf_macros"
+version = "0.11.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3444646e286606587e49f3bcf1679b8cef1dc2c5ecc29ddacaffc305180d464b"
+dependencies = [
+ "phf_generator 0.11.2",
+ "phf_shared 0.11.2",
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
 [[package]]
 name = "phf_shared"
 version = "0.10.0"
@@ -1821,6 +1897,7 @@ dependencies = [
  "debounced",
  "env_logger",
  "futures",
+ "grass",
  "html5ever",
  "log",
  "markup5ever_rcdom",
diff --git a/Cargo.toml b/Cargo.toml
index 7ca9bb1..7680a1a 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -23,6 +23,7 @@ compute_graph = { path = "crates/compute_graph" }
 debounced = "0.2.0"
 env_logger = "0.11.6"
 futures = "0.3.31"
+grass = { version = "0.13.4", default-features = false }
 html5ever = "0.27.0"
 log = "0.4.22"
 markup5ever_rcdom = "0.3.0"
diff --git a/site_test/css/main.scss b/site_test/css/main.scss
new file mode 100644
index 0000000..b6f6b6d
--- /dev/null
+++ b/site_test/css/main.scss
@@ -0,0 +1,5 @@
+.foo {
+    .bar {
+        color: red;
+    }
+}
diff --git a/src/generator/css.rs b/src/generator/css.rs
new file mode 100644
index 0000000..94ef7b0
--- /dev/null
+++ b/src/generator/css.rs
@@ -0,0 +1,90 @@
+use std::{cell::RefCell, collections::HashSet, io::Write, path::PathBuf, rc::Rc};
+
+use compute_graph::{
+    InvalidationSignal,
+    builder::GraphBuilder,
+    rule::{Input, InputVisitable, Rule},
+    synchronicity::Asynchronous,
+};
+use grass::{Fs, Options, OutputStyle};
+use log::error;
+
+use super::{
+    FileWatcher,
+    util::{content_path, output_writer},
+};
+
+pub fn make_graph(
+    builder: &mut GraphBuilder<(), Asynchronous>,
+    watcher: Rc<RefCell<FileWatcher>>,
+) -> Input<()> {
+    let invalidate_css_box = Rc::new(RefCell::new(None));
+    let (css, invalidate_css) = builder.add_invalidatable_rule(CompileScss {
+        watcher,
+        watched: HashSet::new(),
+        invalidate: Rc::clone(&invalidate_css_box),
+    });
+    invalidate_css_box.replace(Some(invalidate_css));
+    css
+}
+
+#[derive(InputVisitable)]
+struct CompileScss {
+    watcher: Rc<RefCell<FileWatcher>>,
+    watched: HashSet<PathBuf>,
+    invalidate: Rc<RefCell<Option<InvalidationSignal>>>,
+}
+impl Rule for CompileScss {
+    type Output = ();
+    fn evaluate(&mut self) -> Self::Output {
+        let read_files = RefCell::new(vec![]);
+        let fs = TrackingFs(&read_files);
+        let style = if cfg!(debug_assertions) {
+            OutputStyle::Expanded
+        } else {
+            OutputStyle::Compressed
+        };
+        let options = Options::default().fs(&fs).style(style);
+        let result = grass::from_path(content_path("css/main.scss"), &options);
+        let mut watcher = self.watcher.borrow_mut();
+        for file in read_files.take() {
+            if !self.watched.contains(&file) {
+                self.watched.insert(file.clone());
+                let signal = self.invalidate.borrow().clone().unwrap();
+                watcher.watch(file, move || signal.invalidate());
+            }
+        }
+        match result {
+            Ok(s) => {
+                output_writer("css/main.css")
+                    .expect("css writer")
+                    .write_all(s.as_bytes())
+                    .expect("writing css");
+            }
+            Err(e) => {
+                error!("Error compiling sass: {:?}", e);
+            }
+        }
+    }
+}
+
+#[derive(Debug)]
+struct TrackingFs<'a>(&'a RefCell<Vec<PathBuf>>);
+impl<'a> Fs for TrackingFs<'a> {
+    fn is_file(&self, path: &std::path::Path) -> bool {
+        path.is_file()
+    }
+
+    fn is_dir(&self, path: &std::path::Path) -> bool {
+        path.is_dir()
+    }
+
+    fn read(&self, path: &std::path::Path) -> std::io::Result<Vec<u8>> {
+        self.0.borrow_mut().push(path.to_owned());
+        std::fs::read(path)
+    }
+
+    fn canonicalize(&self, path: &std::path::Path) -> std::io::Result<PathBuf> {
+        std::fs::canonicalize(path)
+    }
+}
diff --git a/src/generator/markdown.rs b/src/generator/markdown.rs
index 4e3fad9..d074e16 100644
--- a/src/generator/markdown.rs
+++ b/src/generator/markdown.rs
@@ -18,6 +18,7 @@ pub fn parse<'a>(s: &'a str) -> impl Iterator<Item = Event<'a>> {
     options.insert(Options::ENABLE_STRIKETHROUGH);
     options.insert(Options::ENABLE_SMART_PUNCTUATION);
     let parser = Parser::new_ext(s, options);
+    // TODO: revisit which of these stages are necessary, remove unused (and url crate dep)
     let heading_anchors = heading_anchors::new(parser);
     let link_decorations = link_decorations::new(heading_anchors);
     // note backrefs need to come before defs, because the defs stage replaces the
diff --git a/src/generator/mod.rs b/src/generator/mod.rs
index 8f8c25f..046b0ed 100644
--- a/src/generator/mod.rs
+++ b/src/generator/mod.rs
@@ -1,4 +1,5 @@
 mod archive;
+mod css;
 mod markdown;
 mod posts;
 mod tags;
@@ -41,30 +42,23 @@ fn make_graph(watcher: Rc<RefCell<FileWatcher>>) -> anyhow::Result<AsyncGraph<()
         &mut *watcher.borrow_mut(),
     );
 
-    let tag_output = tags::make_graph(
+    let tags = tags::make_graph(
         &mut builder,
         posts,
         default_template,
         &mut *watcher.borrow_mut(),
     );
 
+    let css = css::make_graph(&mut builder, Rc::clone(&watcher));
+
     let post_metadatas_voided = builder.add_rule(MapToVoid(post_metadatas));
     let output = Combine::make(&mut builder, &[
         void_outputs,
         archive,
-        tag_output,
+        tags,
+        css,
         post_metadatas_voided,
     ]);
     builder.set_existing_output(output);
     Ok(builder.build()?)
 }
-
-// #[derive(InputVisitable)]
-// struct Output {
-//     archive: Input<()>,
-//     posts: Input<()>,
-// }
-// impl Rule for Output {
-//     type Output = ();
-//     fn evaluate(&mut self) -> Self::Output {}
-// }
diff --git a/src/generator/util/file_watcher.rs b/src/generator/util/file_watcher.rs
index 6549c6a..064bc8e 100644
--- a/src/generator/util/file_watcher.rs
+++ b/src/generator/util/file_watcher.rs
@@ -1,6 +1,8 @@
 use std::{
+    cell::RefCell,
     collections::HashMap,
     path::{Path, PathBuf},
+    rc::Rc,
 };
 
 use notify::{EventHandler, Watcher};
@@ -10,14 +12,12 @@ use crate::generator::util::content_base_path;
 
 pub struct FileWatcher {
     handlers: HashMap<PathBuf, Box<dyn Fn() -> ()>>,
-    watcher: Option<notify::RecommendedWatcher>,
 }
 
 impl FileWatcher {
     pub fn new() -> Self {
         Self {
             handlers: HashMap::new(),
-            watcher: None,
         }
     }
 
@@ -35,20 +35,18 @@ impl FileWatcher {
         }
     }
 
-    pub async fn start(&mut self) -> anyhow::Result<()> {
-        assert!(self.watcher.is_none());
+    pub async fn start(self_: Rc<RefCell<Self>>) -> anyhow::Result<()> {
         let (tx, mut rx) = tokio::sync::mpsc::unbounded_channel::<notify::Result<notify::Event>>();
 
         let mut watcher = notify::recommended_watcher(AsyncEventHandler(tx))?;
         watcher.watch(&content_base_path(), notify::RecursiveMode::Recursive)?;
-        self.watcher = Some(watcher);
 
         let mut absolute_content_parent = content_base_path().canonicalize()?;
         absolute_content_parent.pop();
 
         while let Some(result) = rx.recv().await {
             if let Ok(ev) = result {
-                self.handle_event(ev, &absolute_content_parent);
+                self_.borrow().handle_event(ev, &absolute_content_parent);
             }
         }
 
diff --git a/src/main.rs b/src/main.rs
index 8ccbbd8..f9d7c7c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -48,15 +48,14 @@ async fn main() {
             if matches.contains_id("watch") {
                 let (tx, rx) = tokio::sync::mpsc::unbounded_channel::<()>();
 
-                let mut watcher = watcher.borrow_mut();
-                watcher.watch(content_base_path(), move || {
+                watcher.borrow_mut().watch(content_base_path(), move || {
                     tx.send(()).expect("sending regenerate signal");
                 });
 
                 let mut debounced =
-                    debounced(UnboundedReceiverStream::new(rx), Duration::from_millis(500));
+                    debounced(UnboundedReceiverStream::new(rx), Duration::from_millis(100));
 
-                let watch = watcher.start().fuse();
+                let watch = FileWatcher::start(watcher).fuse();
 
                 let regenerate = async move {
                     while let Some(_) = debounced.next().await {