diff --git a/src/generate.rs b/src/generate.rs
index ec43d98..7ea0bce 100644
--- a/src/generate.rs
+++ b/src/generate.rs
@@ -4,7 +4,7 @@ mod include_static_helper;
 mod simple_template;
 mod tree;
 
-use std::{collections::HashMap, fmt, ops::ControlFlow, sync::Arc};
+use std::{ops::ControlFlow, sync::Arc};
 
 use atom::FeedDir;
 use dir_helper::DirHelper;
@@ -17,10 +17,14 @@ use crate::{
     config::Config,
     dirs::Dirs,
     fun::seasons::Season,
+    generate::{
+        simple_template::SimpleTemplateDir,
+        tree::{DirIndex, TreehouseDir},
+    },
     sources::Sources,
     vfs::{
-        self, AnchoredAtExt, Cd, Content, ContentCache, Dir, DynDir, Entries, HtmlCanonicalize,
-        MemDir, Overlay, ToDynDir, VPath, VPathBuf,
+        self, layered_dir, AnchoredAtExt, Cd, Content, ContentCache, Dir, DynDir, Entries,
+        HtmlCanonicalize, MemDir, Overlay, ToDynDir, VPath, VPathBuf,
     },
 };
 
@@ -76,134 +80,6 @@ fn load_templates(handlebars: &mut Handlebars, dir: &dyn Dir) {
     });
 }
 
-struct TreehouseDir {
-    dirs: Arc<Dirs>,
-    sources: Arc<Sources>,
-    handlebars: Arc<Handlebars<'static>>,
-    dir_index: DirIndex,
-}
-
-impl TreehouseDir {
-    fn new(
-        dirs: Arc<Dirs>,
-        sources: Arc<Sources>,
-        handlebars: Arc<Handlebars<'static>>,
-        dir_index: DirIndex,
-    ) -> Self {
-        Self {
-            dirs,
-            sources,
-            handlebars,
-            dir_index,
-        }
-    }
-
-    #[instrument("TreehouseDir::dir", skip(self))]
-    fn dir(&self, path: &VPath) -> Vec<VPathBuf> {
-        // NOTE: This does not include simple templates, because that's not really needed right now.
-
-        let mut index = &self.dir_index;
-        for component in path.segments() {
-            if let Some(child) = index.children.get(component) {
-                index = child;
-            } else {
-                // There cannot possibly be any entries under an invalid path.
-                // Bail early.
-                return vec![];
-            }
-        }
-
-        index
-            .children
-            .values()
-            .map(|child| child.full_path.clone())
-            .collect()
-    }
-
-    #[instrument("TreehouseDir::content", skip(self))]
-    fn content(&self, path: &VPath) -> Option<Content> {
-        let path = if path.is_root() {
-            VPath::new_const("index")
-        } else {
-            path
-        };
-
-        self.sources
-            .treehouse
-            .files_by_tree_path
-            .get(path)
-            .map(|&file_id| {
-                Content::new(
-                    "text/html",
-                    tree::generate_or_error(&self.sources, &self.dirs, &self.handlebars, file_id)
-                        .into(),
-                )
-            })
-            .or_else(|| {
-                if path.file_name().is_some_and(|s| !s.starts_with('_')) {
-                    let template_name = path.with_extension("hbs");
-                    if self.handlebars.has_template(template_name.as_str()) {
-                        return Some(Content::new(
-                            "text/html",
-                            simple_template::generate_or_error(
-                                &self.sources,
-                                &self.handlebars,
-                                template_name.as_str(),
-                            )
-                            .into(),
-                        ));
-                    }
-                }
-                None
-            })
-    }
-}
-
-impl Dir for TreehouseDir {
-    fn query(&self, path: &VPath, query: &mut vfs::Query) {
-        query.provide(|| Entries(self.dir(path)));
-        query.try_provide(|| self.content(path));
-    }
-}
-
-impl fmt::Debug for TreehouseDir {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        f.write_str("TreehouseDir")
-    }
-}
-
-/// Acceleration structure for `dir` operations on [`TreehouseDir`]s.
-#[derive(Debug, Default)]
-struct DirIndex {
-    full_path: VPathBuf,
-    children: HashMap<VPathBuf, DirIndex>,
-}
-
-impl DirIndex {
-    #[instrument(name = "DirIndex::new", skip(paths))]
-    pub fn new<'a>(paths: impl Iterator<Item = &'a VPath>) -> Self {
-        let mut root = DirIndex::default();
-
-        for path in paths {
-            let mut parent = &mut root;
-            let mut full_path = VPath::ROOT.to_owned();
-            for segment in path.segments() {
-                full_path.push(segment);
-                let child = parent
-                    .children
-                    .entry(segment.to_owned())
-                    .or_insert_with(|| DirIndex {
-                        full_path: full_path.clone(),
-                        children: HashMap::new(),
-                    });
-                parent = child;
-            }
-        }
-
-        root
-    }
-}
-
 pub fn target(dirs: Arc<Dirs>, sources: Arc<Sources>) -> DynDir {
     let mut handlebars = create_handlebars(&sources.config.site, dirs.static_.clone());
     load_templates(&mut handlebars, &dirs.template);
@@ -226,13 +102,16 @@ pub fn target(dirs: Arc<Dirs>, sources: Arc<Sources>) -> DynDir {
     );
 
     let dir_index = DirIndex::new(sources.treehouse.files_by_tree_path.keys().map(|x| &**x));
-    let tree_view = TreehouseDir::new(dirs, sources, handlebars, dir_index);
+    let treehouse_dir = layered_dir(&[
+        TreehouseDir::new(dirs, sources.clone(), handlebars.clone(), dir_index).to_dyn(),
+        SimpleTemplateDir::new(sources.clone(), handlebars.clone()).to_dyn(),
+    ]);
 
-    let tree_view = ContentCache::new(tree_view);
+    let tree_view = ContentCache::new(treehouse_dir);
     tree_view.warm_up();
     let tree_view = HtmlCanonicalize::new(tree_view);
 
-    Overlay::new(tree_view.to_dyn(), root.to_dyn())
+    layered_dir(&[tree_view.to_dyn(), root.to_dyn()])
         .anchored_at(VPath::ROOT.to_owned())
         .to_dyn()
 }
diff --git a/src/generate/atom.rs b/src/generate/atom.rs
index 9a39f7c..f41bb9b 100644
--- a/src/generate/atom.rs
+++ b/src/generate/atom.rs
@@ -4,8 +4,7 @@ use anyhow::Context;
 use chrono::{DateTime, Utc};
 use handlebars::Handlebars;
 use serde::Serialize;
-use tracing::{info, info_span, instrument};
-use ulid::Ulid;
+use tracing::{info_span, instrument};
 
 use crate::{
     dirs::Dirs,
diff --git a/src/generate/simple_template.rs b/src/generate/simple_template.rs
index 6ed88e6..879485b 100644
--- a/src/generate/simple_template.rs
+++ b/src/generate/simple_template.rs
@@ -1,30 +1,70 @@
+use std::{fmt, sync::Arc};
+
 use anyhow::Context;
 use handlebars::Handlebars;
 use tracing::instrument;
 
-use crate::sources::Sources;
+use crate::{
+    sources::Sources,
+    vfs::{Content, Dir, Query, VPath},
+};
 
 use super::BaseTemplateData;
 
-#[instrument(name = "simple_template::generate", skip(sources, handlebars))]
-pub fn generate(
-    sources: &Sources,
-    handlebars: &Handlebars,
-    template_name: &str,
-) -> anyhow::Result<String> {
-    let base_template_data = BaseTemplateData::new(sources);
-    handlebars
-        .render(template_name, &base_template_data)
-        .context("failed to render template")
+pub struct SimpleTemplateDir {
+    sources: Arc<Sources>,
+    handlebars: Arc<Handlebars<'static>>,
 }
 
-pub fn generate_or_error(
-    sources: &Sources,
-    handlebars: &Handlebars,
-    template_name: &str,
-) -> String {
-    match generate(sources, handlebars, template_name) {
-        Ok(html) => html,
-        Err(error) => format!("error: {error:?}"),
+impl SimpleTemplateDir {
+    pub fn new(sources: Arc<Sources>, handlebars: Arc<Handlebars<'static>>) -> Self {
+        Self {
+            sources,
+            handlebars,
+        }
+    }
+
+    #[instrument(name = "simple_template::generate", skip(self))]
+    fn generate(&self, template_name: &str) -> anyhow::Result<String> {
+        let base_template_data = BaseTemplateData::new(&self.sources);
+        self.handlebars
+            .render(template_name, &base_template_data)
+            .context("failed to render template")
+    }
+
+    fn generate_or_error(&self, template_name: &str) -> String {
+        match self.generate(template_name) {
+            Ok(html) => html,
+            Err(error) => format!("error: {error:?}"),
+        }
+    }
+
+    #[instrument("TreehouseDir::content", skip(self))]
+    fn content(&self, path: &VPath) -> Option<Content> {
+        if path.file_name().is_some_and(|s| !s.starts_with('_')) {
+            let template_name = path.with_extension("hbs");
+            if self.handlebars.has_template(template_name.as_str()) {
+                return Some(Content::new(
+                    "text/html",
+                    self.generate_or_error(template_name.as_str()).into(),
+                ));
+            }
+        }
+
+        None
+    }
+}
+
+impl Dir for SimpleTemplateDir {
+    fn query(&self, path: &VPath, query: &mut Query) {
+        // NOTE: An implementation of Entries is not currently provided, because SimpleTemplateDir
+        // isn't used enough to need one.
+        query.try_provide(|| self.content(path));
+    }
+}
+
+impl fmt::Debug for SimpleTemplateDir {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str("SimpleTemplateDir")
     }
 }
diff --git a/src/generate/tree.rs b/src/generate/tree.rs
index 9fc77aa..9ecd14c 100644
--- a/src/generate/tree.rs
+++ b/src/generate/tree.rs
@@ -1,3 +1,5 @@
+use std::{collections::HashMap, fmt, sync::Arc};
+
 use anyhow::{ensure, Context};
 use handlebars::Handlebars;
 use serde::Serialize;
@@ -5,10 +7,11 @@ use tracing::{info_span, instrument};
 
 use crate::{
     dirs::Dirs,
-    generate::BaseTemplateData,
+    generate::{simple_template, BaseTemplateData},
     html::{breadcrumbs::breadcrumbs_to_html, tree},
     sources::Sources,
     state::FileId,
+    vfs::{self, Content, Dir, Entries, VPath, VPathBuf},
 };
 
 #[derive(Serialize)]
@@ -109,3 +112,113 @@ pub fn generate_or_error(
         Err(error) => format!("error: {error:?}"),
     }
 }
+
+pub struct TreehouseDir {
+    dirs: Arc<Dirs>,
+    sources: Arc<Sources>,
+    handlebars: Arc<Handlebars<'static>>,
+    dir_index: DirIndex,
+}
+
+impl TreehouseDir {
+    pub fn new(
+        dirs: Arc<Dirs>,
+        sources: Arc<Sources>,
+        handlebars: Arc<Handlebars<'static>>,
+        dir_index: DirIndex,
+    ) -> Self {
+        Self {
+            dirs,
+            sources,
+            handlebars,
+            dir_index,
+        }
+    }
+
+    #[instrument("TreehouseDir::dir", skip(self))]
+    fn dir(&self, path: &VPath) -> Vec<VPathBuf> {
+        // NOTE: This does not include simple templates, because that's not really needed right now.
+
+        let mut index = &self.dir_index;
+        for component in path.segments() {
+            if let Some(child) = index.children.get(component) {
+                index = child;
+            } else {
+                // There cannot possibly be any entries under an invalid path.
+                // Bail early.
+                return vec![];
+            }
+        }
+
+        index
+            .children
+            .values()
+            .map(|child| child.full_path.clone())
+            .collect()
+    }
+
+    #[instrument("TreehouseDir::content", skip(self))]
+    fn content(&self, path: &VPath) -> Option<Content> {
+        let path = if path.is_root() {
+            VPath::new_const("index")
+        } else {
+            path
+        };
+
+        self.sources
+            .treehouse
+            .files_by_tree_path
+            .get(path)
+            .map(|&file_id| {
+                Content::new(
+                    "text/html",
+                    generate_or_error(&self.sources, &self.dirs, &self.handlebars, file_id).into(),
+                )
+            })
+    }
+}
+
+impl Dir for TreehouseDir {
+    fn query(&self, path: &VPath, query: &mut vfs::Query) {
+        query.provide(|| Entries(self.dir(path)));
+        query.try_provide(|| self.content(path));
+    }
+}
+
+impl fmt::Debug for TreehouseDir {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str("TreehouseDir")
+    }
+}
+
+/// Acceleration structure for `dir` operations on [`TreehouseDir`]s.
+#[derive(Debug, Default)]
+pub struct DirIndex {
+    full_path: VPathBuf,
+    children: HashMap<VPathBuf, DirIndex>,
+}
+
+impl DirIndex {
+    #[instrument(name = "DirIndex::new", skip(paths))]
+    pub fn new<'a>(paths: impl Iterator<Item = &'a VPath>) -> Self {
+        let mut root = DirIndex::default();
+
+        for path in paths {
+            let mut parent = &mut root;
+            let mut full_path = VPath::ROOT.to_owned();
+            for segment in path.segments() {
+                full_path.push(segment);
+                let child = parent
+                    .children
+                    .entry(segment.to_owned())
+                    .or_insert_with(|| DirIndex {
+                        full_path: full_path.clone(),
+                        children: HashMap::new(),
+                    });
+                parent = child;
+            }
+        }
+
+        root
+    }
+}
diff --git a/src/vfs.rs b/src/vfs.rs
index 7d9c6b4..772592e 100644
--- a/src/vfs.rs
+++ b/src/vfs.rs
@@ -168,6 +168,12 @@ impl<'a> dyn Erased<'a> + 'a {
     }
 }
 
+impl Dir for () {
+    fn query(&self, _path: &VPath, _query: &mut Query) {
+        // Noop implementation.
+    }
+}
+
 impl<T> Dir for &T
 where
     T: Dir,
diff --git a/src/vfs/html_canonicalize.rs b/src/vfs/html_canonicalize.rs
index fb3ee54..bd3e772 100644
--- a/src/vfs/html_canonicalize.rs
+++ b/src/vfs/html_canonicalize.rs
@@ -2,6 +2,7 @@ use core::fmt;
 
 use super::{Dir, Query, VPath};
 
+/// This Dir exists to serve as a compatibility layer for very old links that end with .html.
 pub struct HtmlCanonicalize<T> {
     inner: T,
 }
diff --git a/src/vfs/overlay.rs b/src/vfs/overlay.rs
index 13907ed..470a076 100644
--- a/src/vfs/overlay.rs
+++ b/src/vfs/overlay.rs
@@ -2,6 +2,8 @@ use std::fmt;
 
 use tracing::instrument;
 
+use crate::vfs::ToDynDir;
+
 use super::{entries, Dir, DynDir, Entries, Query, VPath, VPathBuf};
 
 pub struct Overlay {
@@ -38,3 +40,18 @@ impl fmt::Debug for Overlay {
         write!(f, "Overlay({:?}, {:?})", self.base, self.overlay)
     }
 }
+
+pub fn layered_dir(layers: &[DynDir]) -> DynDir {
+    match layers {
+        [] => ().to_dyn(),
+        [dir] => dir.clone(),
+        [left, right] => Overlay::new(left.clone(), right.clone()).to_dyn(),
+        [left, right, rest @ ..] => {
+            let mut overlay = Overlay::new(left.clone(), right.clone());
+            for dir in rest {
+                overlay = Overlay::new(overlay.to_dyn(), dir.clone());
+            }
+            overlay.to_dyn()
+        }
+    }
+}