diff --git a/src/code.rs b/src/code.rs
index f4883f6..1c72952 100644
--- a/src/code.rs
+++ b/src/code.rs
@@ -1,53 +1,65 @@
+/// TODO: Documentation
+
 use std::io::{self, Write};
 use std::ops::AddAssign;
 
+// TODO: Documentation
 #[derive(Clone, PartialEq, Eq)]
 pub enum Direction {
     Clockwise,
     AntiClockwise,
 }
 
+// TODO: Documentation
 #[derive(Copy, Clone, PartialEq, Eq)]
 pub enum Tool {
     Off,
     On,
 }
 
+// TODO: Documentation
 #[derive(Clone, PartialEq)]
 pub enum Distance {
     Absolute,
     Incremental,
 }
 
+// TODO: Documentation
 #[derive(Default, PartialEq, Clone)]
 pub struct Program(Vec<GCode>);
 
+// TODO: Documentation
 impl std::ops::Deref for Program {
     type Target = [GCode];
 
+    // TODO: Documentation
     fn deref(&self) -> &Self::Target {
         self.0.deref()
     }
 }
 
+// TODO: Documentation
 impl AddAssign for Program {
     fn add_assign(&mut self, mut other: Program) {
         self.0.extend(other.0.drain(..));
     }
 }
 
+// TODO: Documentation
 impl From<Vec<GCode>> for Program {
     fn from(v: Vec<GCode>) -> Self {
         Self(v)
     }
 }
 
+// TODO: Documentation
 impl Program {
     pub fn push(&mut self, g: GCode) {
         self.0.push(g)
     }
 }
 
+// TODO: Documentation
 macro_rules! write_if_some {
     ($w:expr, $s:expr, $v:ident) => {
         if let Some(v) = $v {
@@ -58,6 +70,7 @@ macro_rules! write_if_some {
     };
 }
 
+// TODO: Documentation
 // Rudimentary regular expression GCode validator.
 pub fn validate_gcode(gcode: &&str) -> bool {
     use regex::Regex;
@@ -65,6 +78,7 @@ pub fn validate_gcode(gcode: &&str) -> bool {
     gcode.lines().all(|line| re.is_match(line))
 }
 
+// TODO: Documentation
 #[derive(Clone, PartialEq)]
 pub enum GCode {
     RapidPositioning {
@@ -93,6 +107,8 @@ pub enum GCode {
     Raw(Box<String>),
 }
 
+// TODO: Documentation
+// TODO: This function is too large
 pub fn program2gcode<W: Write>(p: &Program, mut w: W) -> io::Result<()> {
     use GCode::*;
     let mut last_feedrate: Option<f64> = None;
diff --git a/src/machine.rs b/src/machine.rs
index 92ff56f..b6e1c6c 100644
--- a/src/machine.rs
+++ b/src/machine.rs
@@ -4,6 +4,7 @@
 
 use crate::code::*;
 
+// TODO: Documentation
 // Generic machine state simulation, assuming nothing is known about the machine when initialized.
 pub struct Machine {
     tool_state: Option<Tool>,
@@ -12,6 +13,7 @@ pub struct Machine {
     pub tool_off_action: Vec<GCode>,
 }
 
+// TODO: Documentation
 // Assigns reasonable default settings that apply to most gcode applications.
 impl Default for Machine {
     fn default() -> Self {
@@ -38,7 +40,8 @@ impl Default for Machine {
     }
 }
 
-// Implements the state machine functions
+// TODO: Documentation
+// Implements the state machine functions to export Gcode.
 impl Machine {
     // Outputs gcode to turn the tool on.
     pub fn tool_on(&mut self) -> Vec<GCode> {
diff --git a/src/main.rs b/src/main.rs
index 7ef45cb..21e887c 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,5 @@
+/// TODO: documentation
+
 #[macro_use]
 extern crate clap;
 extern crate env_logger;
@@ -23,6 +25,7 @@ use code::*;
 use machine::*;
 use turtle::*;
 
+// TODO: Documentation
 fn main() -> io::Result<()> {
     if env::var("RUST_LOG").is_err() {
         env::set_var("RUST_LOG", "svg2gcode=info")
@@ -82,12 +85,14 @@ fn main() -> io::Result<()> {
     program2gcode(&prog, File::create("out.gcode")?)
 }
 
+// TODO: Documentation
 struct ProgramOptions {
     tolerance: f64,
     feedrate: f64,
     dpi: f64,
 }
 
+// Sets the baseline options for the machine.
 impl Default for ProgramOptions {
     fn default() -> Self {
         ProgramOptions {
@@ -98,6 +103,8 @@ impl Default for ProgramOptions {
     }
 }
 
+// TODO: Documentation
+// TODO: This function is much too large
 fn svg2program(doc: &svgdom::Document, opts: ProgramOptions, mach: Machine) -> Program {
     let mut p = Program::default();
     let mut t = Turtle::from(mach);
@@ -289,6 +296,7 @@ fn svg2program(doc: &svgdom::Document, opts: ProgramOptions, mach: Machine) -> P
     p
 }
 
+// TODO: Documentation
 fn length_to_mm(l: svgdom::Length, dpi: f64) -> f64 {
     use svgdom::LengthUnit::*;
     use uom::si::f64::Length;
diff --git a/src/turtle.rs b/src/turtle.rs
index 1e8de06..cc97954 100644
--- a/src/turtle.rs
+++ b/src/turtle.rs
@@ -1,12 +1,14 @@
+/// TODO: Documentation
+
 use crate::code::GCode;
 use crate::machine::Machine;
 use lyon_geom::euclid::{Angle, default::Transform2D};
 use lyon_geom::math::{point, vector, F64Point};
 use lyon_geom::{ArcFlags, CubicBezierSegment, QuadraticBezierSegment, SvgArc};
 
-/// Turtle graphics simulator for paths that outputs the GCode enum representation for each operation.
-/// Handles trasforms, scaling, position offsets, etc.
-/// See https://www.w3.org/TR/SVG/paths.html
+/// Turtle graphics simulator for paths that outputs the GCode enum
+/// representation for each operation.  Handles trasforms, scaling, position
+/// offsets, etc.  See https://www.w3.org/TR/SVG/paths.html
 pub struct Turtle {
     curpos: F64Point,
     initpos: F64Point,
@@ -17,6 +19,7 @@ pub struct Turtle {
     prev_ctrl: Option<F64Point>,
 }
 
+// TODO: Documentation
 impl Default for Turtle {
     fn default() -> Self {
         Self {
@@ -31,6 +34,7 @@ impl Default for Turtle {
     }
 }
 
+// TODO: Documentation
 impl From<Machine> for Turtle {
     fn from(m: Machine) -> Self {
         let mut t = Self::default();
@@ -39,6 +43,7 @@ impl From<Machine> for Turtle {
     }
 }
 
+// TODO: Documentation
 impl Turtle {
     pub fn move_to<X, Y>(&mut self, abs: bool, x: X, y: Y) -> Vec<GCode>
     where
@@ -75,12 +80,14 @@ impl Turtle {
         .collect()
     }
 
+    // TODO: Documentation
     pub fn close<Z, F>(&mut self, z: Z, f: F) -> Vec<GCode>
     where
         Z: Into<Option<f64>>,
         F: Into<Option<f64>>,
     {
-        // See https://www.w3.org/TR/SVG/paths.html#Segment-CompletingClosePath which could result in a G91 G1 X0 Y0
+        // See https://www.w3.org/TR/SVG/paths.html#Segment-CompletingClosePath
+        // which could result in a G91 G1 X0 Y0
         if (self.curpos - self.initpos)
             .abs()
             .lower_than(vector(std::f64::EPSILON, std::f64::EPSILON))
@@ -104,6 +111,7 @@ impl Turtle {
         .collect()
     }
 
+    // TODO: Documentation
     pub fn line<X, Y, Z, F>(&mut self, abs: bool, x: X, y: Y, z: Z, f: F) -> Vec<GCode>
     where
         X: Into<Option<f64>>,
@@ -176,6 +184,7 @@ impl Turtle {
             .collect()
     }
 
+    // TODO: Documentation
     pub fn cubic_bezier<Z, F>(
         &mut self,
         abs: bool,
@@ -217,6 +226,7 @@ impl Turtle {
         self.bezier(cbs, tolerance, z, f)
     }
 
+    // TODO: Documentation
     pub fn smooth_cubic_bezier<Z, F>(
         &mut self,
         abs: bool,
@@ -254,6 +264,7 @@ impl Turtle {
         self.bezier(cbs, tolerance, z, f)
     }
 
+    // TODO: Documentation
     pub fn smooth_quadratic_bezier<Z, F>(
         &mut self,
         abs: bool,
@@ -281,6 +292,7 @@ impl Turtle {
         self.bezier(qbs.to_cubic(), tolerance, z, f)
     }
 
+    // TODO: Documentation
     pub fn quadratic_bezier<Z, F>(
         &mut self,
         abs: bool,
@@ -312,6 +324,7 @@ impl Turtle {
         self.bezier(qbs.to_cubic(), tolerance, z, f)
     }
 
+    // TODO: Documentation
     pub fn elliptical<Z, F>(
         &mut self,
         abs: bool,
@@ -377,6 +390,7 @@ impl Turtle {
             .collect()
     }
 
+    // TODO: Documentation
     pub fn stack_scaling(&mut self, scaling: Transform2D<f64>) {
         self.curtran = self.curtran.post_transform(&scaling);
         if let Some(ref current_scaling) = self.scaling {
@@ -386,6 +400,7 @@ impl Turtle {
         }
     }
 
+    // TODO: Documentation
     pub fn push_transform(&mut self, trans: Transform2D<f64>) {
         self.transtack.push(self.curtran);
         if let Some(ref scaling) = self.scaling {
@@ -399,6 +414,7 @@ impl Turtle {
         }
     }
 
+    // TODO: Documentation
     pub fn pop_transform(&mut self) {
         self.curtran = self
             .transtack
@@ -406,6 +422,7 @@ impl Turtle {
             .expect("popped when no transforms left");
     }
 
+    // TODO: Documentation
     pub fn reset(&mut self) {
         self.curpos = point(0.0, 0.0);
         self.curpos = self.curtran.transform_point(self.curpos);