diff --git a/Cargo.lock b/Cargo.lock
index 5b55075..6783465 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -122,6 +122,21 @@ version = "1.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cdb031dd78e28731d87d56cc8ffef4a8f36ca26c38fe2de700543e627f8a464a"
 
+[[package]]
+name = "base64"
+version = "0.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "904dfeac50f3cdaba28fc6f57fdcddb75f49ed61346676a78c4ffe55877802fd"
+
+[[package]]
+name = "bincode"
+version = "1.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b1f45e9417d87227c7a56d22e471c6206462cba514c7590c09aff4cf6d1ddcad"
+dependencies = [
+ "serde",
+]
+
 [[package]]
 name = "bit-set"
 version = "0.5.2"
@@ -225,6 +240,16 @@ dependencies = [
  "num-traits",
 ]
 
+[[package]]
+name = "chrono"
+version = "0.4.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "670ad68c9088c2a963aaa298cb369688cf3f9465ce5e2d4ca10e6e0098a1ce73"
+dependencies = [
+ "num-integer",
+ "num-traits",
+]
+
 [[package]]
 name = "cocoa"
 version = "0.24.0"
@@ -633,6 +658,16 @@ dependencies = [
  "egui",
 ]
 
+[[package]]
+name = "fancy-regex"
+version = "0.7.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9d6b8560a05112eb52f04b00e5d3790c0dd75d9d980eb8a122fb23b92a623ccf"
+dependencies = [
+ "bit-set",
+ "regex",
+]
+
 [[package]]
 name = "filetime"
 version = "0.2.15"
@@ -645,6 +680,18 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "flate2"
+version = "1.0.22"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e6988e897c1c9c485f43b47a529cef42fde0547f9d8d41a7062518f1d8fc53f"
+dependencies = [
+ "cfg-if 1.0.0",
+ "crc32fast",
+ "libc",
+ "miniz_oxide 0.4.4",
+]
+
 [[package]]
 name = "fnv"
 version = "1.0.7"
@@ -959,6 +1006,12 @@ dependencies = [
  "web-sys",
 ]
 
+[[package]]
+name = "itoa"
+version = "0.4.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b71991ff56294aa922b450139ee08b3bfc70982c6b2c7562771375cf73542dd4"
+
 [[package]]
 name = "jni-sys"
 version = "0.3.0"
@@ -1019,6 +1072,12 @@ version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e2abad23fbc42b3700f2f279844dc832adb2b2eb069b2df918f455c4e18cc646"
 
+[[package]]
+name = "lazycell"
+version = "1.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "830d08ce1d1d941e6b30645f1a0eb5643013d835ce3779a5fc208261dbe10f55"
+
 [[package]]
 name = "libc"
 version = "0.2.101"
@@ -1045,6 +1104,21 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "line-wrap"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f30344350a2a51da54c1d53be93fade8a237e545dbcc4bdbe635413f2117cab9"
+dependencies = [
+ "safemem",
+]
+
+[[package]]
+name = "linked-hash-map"
+version = "0.5.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7fb9b38af92608140b86b693604b9ffcc5824240a484d1ecd4795bacb2fe88f3"
+
 [[package]]
 name = "linon"
 version = "0.1.0"
@@ -1062,6 +1136,7 @@ dependencies = [
  "image",
  "log",
  "notify",
+ "syntect",
  "tobj",
  "wasm-bindgen",
  "wasm-bindgen-futures",
@@ -1496,6 +1571,20 @@ version = "0.3.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3831453b3449ceb48b6d9c7ad7c96d5ea673e9b470a1dc578c2ce6521230884c"
 
+[[package]]
+name = "plist"
+version = "1.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a38d026d73eeaf2ade76309d0c65db5a35ecf649e3cec428db316243ea9d6711"
+dependencies = [
+ "base64",
+ "chrono",
+ "indexmap",
+ "line-wrap",
+ "serde",
+ "xml-rs",
+]
+
 [[package]]
 name = "png"
 version = "0.16.8"
@@ -1645,6 +1734,18 @@ dependencies = [
  "owned_ttf_parser 0.6.0",
 ]
 
+[[package]]
+name = "ryu"
+version = "1.0.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "71d301d4193d031abdd79ff7e3dd721168a9572ef3fe51a1517aba235bd8f86e"
+
+[[package]]
+name = "safemem"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ef703b7cb59335eae2eb93ceb664c0eb7ea6bf567079d843e09420219668e072"
+
 [[package]]
 name = "same-file"
 version = "1.0.6"
@@ -1678,6 +1779,28 @@ version = "1.0.130"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "f12d06de37cf59146fbdecab66aa99f9fe4f78722e3607577a5375d66bd0c913"
 
+[[package]]
+name = "serde_derive"
+version = "1.0.130"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d7bc1a1ab1961464eae040d96713baa5a724a8152c1222492465b54322ec508b"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn",
+]
+
+[[package]]
+name = "serde_json"
+version = "1.0.69"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e466864e431129c7e0d3476b92f20458e5879919a0596c6472738d9fa2d342f8"
+dependencies = [
+ "itoa",
+ "ryu",
+ "serde",
+]
+
 [[package]]
 name = "slab"
 version = "0.4.4"
@@ -1745,6 +1868,28 @@ dependencies = [
  "unicode-xid",
 ]
 
+[[package]]
+name = "syntect"
+version = "4.6.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8b20815bbe80ee0be06e6957450a841185fcf690fe0178f14d77a05ce2caa031"
+dependencies = [
+ "bincode",
+ "bitflags",
+ "fancy-regex",
+ "flate2",
+ "fnv",
+ "lazy_static",
+ "lazycell",
+ "plist",
+ "regex-syntax",
+ "serde",
+ "serde_derive",
+ "serde_json",
+ "walkdir",
+ "yaml-rust",
+]
+
 [[package]]
 name = "termcolor"
 version = "1.1.2"
@@ -2191,3 +2336,12 @@ name = "xml-rs"
 version = "0.8.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "d2d7d3948613f75c98fd9328cfdcc45acc4d360655289d0a7d4ec931392200a3"
+
+[[package]]
+name = "yaml-rust"
+version = "0.4.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "56c1936c4cc7a1c9ab21a1ebb602eb942ba868cbd44a99cb7cdc5892335e1c85"
+dependencies = [
+ "linked-hash-map",
+]
diff --git a/Cargo.toml b/Cargo.toml
index f940fe0..77ec69b 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -19,6 +19,7 @@ tobj = "3.0"
 egui = "0.15"
 egui_winit_platform = "0.11"
 wgpu = "0.11"
+syntect = { version = "4", default-features = false, features = ["default-fancy"] }
 
 [target.'cfg(not(target_arch = "wasm32"))'.dependencies]
 notify = "5.0.0-pre.13"
diff --git a/src/application.rs b/src/application.rs
index 7c319d3..4611a62 100644
--- a/src/application.rs
+++ b/src/application.rs
@@ -4,6 +4,7 @@ use crate::cornell_box as cbox;
 use crate::functions::PredefinedFunction;
 use crate::main_view::{MainView, Settings};
 use crate::reference_view::ReferenceView;
+use crate::syntax_highlighting::code_view_ui;
 use crate::vertices::{get_center, normalize_vertices};
 use anyhow::{Context, Result};
 use wgpu::util::DeviceExt;
@@ -451,7 +452,7 @@ impl Application {
                 });
             ui.vertical(|ui| {
                 ui.label("Custom function:");
-                if ui.code_editor(field_function).lost_focus() {
+                if code_view_ui(ui, field_function).lost_focus() {
                     *predefined_function = PredefinedFunction::Custom;
                     field_function_changed = true;
                 }
diff --git a/src/main.rs b/src/main.rs
index 5b0c14b..ab6e63b 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -5,6 +5,7 @@ mod functions;
 mod main_view;
 mod ray_samples;
 mod reference_view;
+mod syntax_highlighting;
 mod texture;
 mod vertices;
 
diff --git a/src/syntax_highlighting.rs b/src/syntax_highlighting.rs
new file mode 100644
index 0000000..577da88
--- /dev/null
+++ b/src/syntax_highlighting.rs
@@ -0,0 +1,195 @@
+// Based on https://github.com/emilk/egui/blob/0.15.0/egui_demo_lib/src/syntax_highlighting.rs
+// MIT License
+use egui::text::LayoutJob;
+
+/// View some code with syntax highlighing and selection.
+pub fn code_view_ui<S: egui::TextBuffer>(ui: &mut egui::Ui, code: &mut S) -> egui::Response {
+    let language = "rs";
+    let theme = CodeTheme::from_memory(ui.ctx());
+
+    let mut layouter = |ui: &egui::Ui, string: &str, _wrap_width: f32| {
+        let layout_job = highlight(ui.ctx(), &theme, string, language);
+        ui.fonts().layout_job(layout_job)
+    };
+
+    egui::ScrollArea::vertical().show(ui, |ui| {
+        ui.add(
+            egui::TextEdit::multiline(code)
+                .text_style(egui::TextStyle::Monospace)
+                .code_editor()
+                .desired_rows(10)
+                .lock_focus(true)
+                .layouter(&mut layouter),
+        )
+    })
+}
+
+/// Memoized Code highlighting
+pub fn highlight(ctx: &egui::Context, theme: &CodeTheme, code: &str, language: &str) -> LayoutJob {
+    impl egui::util::cache::ComputerMut<(&CodeTheme, &str, &str), LayoutJob> for Highligher {
+        fn compute(&mut self, (theme, code, lang): (&CodeTheme, &str, &str)) -> LayoutJob {
+            self.highlight(theme, code, lang)
+        }
+    }
+
+    type HighlightCache<'a> = egui::util::cache::FrameCache<LayoutJob, Highligher>;
+
+    let mut memory = ctx.memory();
+    let highlight_cache = memory.caches.cache::<HighlightCache<'_>>();
+    highlight_cache.get((theme, code, language))
+}
+
+// ----------------------------------------------------------------------------
+
+#[derive(Clone, Copy, Hash, PartialEq)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+enum SyntectTheme {
+    Base16MochaDark,
+    SolarizedLight,
+}
+
+impl SyntectTheme {
+    fn syntect_key_name(&self) -> &'static str {
+        match self {
+            Self::Base16MochaDark => "base16-mocha.dark",
+            Self::SolarizedLight => "Solarized (light)",
+        }
+    }
+}
+
+#[derive(Clone, Copy, Hash, PartialEq)]
+#[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+#[cfg_attr(feature = "serde", serde(default))]
+pub struct CodeTheme {
+    dark_mode: bool,
+
+    syntect_theme: SyntectTheme,
+}
+
+impl Default for CodeTheme {
+    fn default() -> Self {
+        Self::dark()
+    }
+}
+
+impl CodeTheme {
+    pub fn from_memory(ctx: &egui::Context) -> Self {
+        if ctx.style().visuals.dark_mode {
+            *ctx.memory()
+                .id_data
+                .get_or_insert_with(egui::Id::new("dark"), CodeTheme::dark)
+        } else {
+            *ctx.memory()
+                .id_data
+                .get_or_insert_with(egui::Id::new("light"), CodeTheme::light)
+        }
+    }
+}
+
+impl CodeTheme {
+    pub fn dark() -> Self {
+        Self {
+            dark_mode: true,
+            syntect_theme: SyntectTheme::Base16MochaDark,
+        }
+    }
+
+    pub fn light() -> Self {
+        Self {
+            dark_mode: false,
+            syntect_theme: SyntectTheme::SolarizedLight,
+        }
+    }
+}
+
+// ----------------------------------------------------------------------------
+
+struct Highligher {
+    ps: syntect::parsing::SyntaxSet,
+    ts: syntect::highlighting::ThemeSet,
+}
+
+impl Default for Highligher {
+    fn default() -> Self {
+        Self {
+            ps: syntect::parsing::SyntaxSet::load_defaults_newlines(),
+            ts: syntect::highlighting::ThemeSet::load_defaults(),
+        }
+    }
+}
+
+impl Highligher {
+    #[allow(clippy::unused_self, clippy::unnecessary_wraps)]
+    fn highlight(&self, theme: &CodeTheme, code: &str, lang: &str) -> LayoutJob {
+        self.highlight_impl(theme, code, lang).unwrap_or_else(|| {
+            // Fallback:
+            LayoutJob::simple(
+                code.into(),
+                egui::TextStyle::Monospace,
+                if theme.dark_mode {
+                    egui::Color32::LIGHT_GRAY
+                } else {
+                    egui::Color32::DARK_GRAY
+                },
+                f32::INFINITY,
+            )
+        })
+    }
+
+    fn highlight_impl(&self, theme: &CodeTheme, text: &str, language: &str) -> Option<LayoutJob> {
+        use syntect::easy::HighlightLines;
+        use syntect::highlighting::FontStyle;
+        use syntect::util::LinesWithEndings;
+
+        let syntax = self
+            .ps
+            .find_syntax_by_name(language)
+            .or_else(|| self.ps.find_syntax_by_extension(language))?;
+
+        let theme = theme.syntect_theme.syntect_key_name();
+        let mut h = HighlightLines::new(syntax, &self.ts.themes[theme]);
+
+        use egui::text::{LayoutSection, TextFormat};
+
+        let mut job = LayoutJob {
+            text: text.into(),
+            ..Default::default()
+        };
+
+        for line in LinesWithEndings::from(text) {
+            for (style, range) in h.highlight(line, &self.ps) {
+                let fg = style.foreground;
+                let text_color = egui::Color32::from_rgb(fg.r, fg.g, fg.b);
+                let italics = style.font_style.contains(FontStyle::ITALIC);
+                let underline = style.font_style.contains(FontStyle::ITALIC);
+                let underline = if underline {
+                    egui::Stroke::new(1.0, text_color)
+                } else {
+                    egui::Stroke::none()
+                };
+                job.sections.push(LayoutSection {
+                    leading_space: 0.0,
+                    byte_range: as_byte_range(text, range),
+                    format: TextFormat {
+                        style: egui::TextStyle::Monospace,
+                        color: text_color,
+                        italics,
+                        underline,
+                        ..Default::default()
+                    },
+                });
+            }
+        }
+
+        Some(job)
+    }
+}
+
+fn as_byte_range(whole: &str, range: &str) -> std::ops::Range<usize> {
+    let whole_start = whole.as_ptr() as usize;
+    let range_start = range.as_ptr() as usize;
+    assert!(whole_start <= range_start);
+    assert!(range_start + range.len() <= whole_start + whole.len());
+    let offset = range_start - whole_start;
+    offset..(offset + range.len())
+}