diff --git a/src/code.rs b/src/code.rs
index dcf81ce..f4883f6 100644
--- a/src/code.rs
+++ b/src/code.rs
@@ -58,7 +58,7 @@ macro_rules! write_if_some {
     };
 }
 
-/// Rudimentary regular expression GCode validator.
+// Rudimentary regular expression GCode validator.
 pub fn validate_gcode(gcode: &&str) -> bool {
     use regex::Regex;
     let re = Regex::new(r##"^(?:(?:%|\(.*\)|(?:[A-Z^E^U][+-]?\d+(?:\.\d*)?))\h*)*$"##).unwrap();
diff --git a/src/machine.rs b/src/machine.rs
index 5e03a40..92ff56f 100644
--- a/src/machine.rs
+++ b/src/machine.rs
@@ -1,6 +1,10 @@
+/// State machine used to generate gcode for various operations.
+///
+/// TODO: more detailed examples
+
 use crate::code::*;
 
-/// Generic machine state simulation, assuming nothing is known about the machine when initialized.
+// Generic machine state simulation, assuming nothing is known about the machine when initialized.
 pub struct Machine {
     tool_state: Option<Tool>,
     distance_mode: Option<Distance>,
@@ -8,6 +12,7 @@ pub struct Machine {
     pub tool_off_action: Vec<GCode>,
 }
 
+// Assigns reasonable default settings that apply to most gcode applications.
 impl Default for Machine {
     fn default() -> Self {
         Self {
@@ -33,7 +38,9 @@ impl Default for Machine {
     }
 }
 
+// Implements the state machine functions
 impl Machine {
+    // Outputs gcode to turn the tool on.
     pub fn tool_on(&mut self) -> Vec<GCode> {
         if self.tool_state == Some(Tool::Off) || self.tool_state == None {
             self.tool_state = Some(Tool::On);
@@ -43,6 +50,7 @@ impl Machine {
         }
     }
 
+    // Outputs gcode to turn the tool off.
     pub fn tool_off(&mut self) -> Vec<GCode> {
         if self.tool_state == Some(Tool::On) || self.tool_state == None {
             self.tool_state = Some(Tool::Off);
@@ -52,6 +60,7 @@ impl Machine {
         }
     }
 
+    // Outputs gcode for how distance should be measured: relative or absolute.
     pub fn distance(&mut self, is_absolute: bool) -> Vec<GCode> {
         if is_absolute {
             self.absolute()
@@ -60,6 +69,7 @@ impl Machine {
         }
     }
 
+    // Outputs gcode command to use absolute motion
     pub fn absolute(&mut self) -> Vec<GCode> {
         if self.distance_mode == Some(Distance::Incremental) || self.distance_mode == None {
             self.distance_mode = Some(Distance::Absolute);
@@ -69,6 +79,7 @@ impl Machine {
         }
     }
 
+    // Outputs gcode command to use relative motion
     pub fn incremental(&mut self) -> Vec<GCode> {
         if self.distance_mode == Some(Distance::Absolute) || self.distance_mode == None {
             self.distance_mode = Some(Distance::Incremental);