diff --git a/src/args.rs b/src/args.rs
new file mode 100644
index 0000000..9665dec
--- /dev/null
+++ b/src/args.rs
@@ -0,0 +1,172 @@
+use crate::mushroom;
+use clap::Parser;
+
+#[derive(Parser, Debug, Clone)]
+#[command(version, about, long_about = None)]
+pub struct Args {
+    /// File to save too.
+    #[arg(long, default_value = "mesh.stl")]
+    pub output: String,
+
+    /// Height of total mushroom in millimeters.
+    #[arg(long, default_value_t = 100)]
+    pub height: u32,
+
+    /// Stalk height in millimeters. Zero for default.
+    #[arg(long, default_value_t = 0)]
+    pub stalk_h: u32,
+
+    /// Stalk diameter in millimeters. Zero for default.
+    #[arg(long, default_value_t = 0)]
+    pub stalk_d: u32,
+
+    /// Cap height in millimeters. Zero for default.
+    #[arg(long, default_value_t = 0)]
+    pub cap_h: u32,
+
+    /// Stalk diameter in millimeters. Zero for default.
+    #[arg(long, default_value_t = 0)]
+    pub cap_d: u32,
+
+    /// Shape of the cap.
+    #[arg(long, default_value_t, value_enum)]
+    pub cap_style: mushroom::CapStyle,
+}
+
+impl Args {
+    pub fn mushroom_from_args(&self) -> mushroom::Mushroom {
+        // Default values are all based on height.
+        let stalk_h: f32 = if self.stalk_h != 0 {
+            self.stalk_h as f32
+        } else {
+            if self.cap_h != 0 {
+                (self.height - self.cap_h) as f32
+            } else {
+                self.height as f32 * 0.66
+            }
+        };
+        let stalk_r: f32 = if self.stalk_d != 0 {
+            self.stalk_d as f32
+        } else {
+            self.height as f32 / 10.
+        } / 2.0; // computer the diamter, and convert to radius.
+        let cap_h: f32 = if self.cap_h != 0 {
+            self.cap_h as f32
+        } else {
+            self.height as f32 - stalk_h
+        };
+        let cap_r: f32 = if self.cap_d != 0 {
+            self.cap_d as f32
+        } else {
+            self.height as f32
+        } / 2.0; // computer the diamter, and convert to radius.
+
+        let cap_style = self.cap_style.clone();
+
+        mushroom::Mushroom {
+            stalk_h,
+            stalk_r,
+            cap_h,
+            cap_r,
+            cap_style,
+        }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::ffi::OsString;
+
+    fn validate_mushroom_from_args<I, T>(
+        string_args: I,
+        stalk_h: f32,
+        stalk_r: f32,
+        cap_h: f32,
+        cap_r: f32,
+        cap_style: mushroom::CapStyle,
+    ) where
+        I: IntoIterator<Item = T>,
+        T: Into<OsString> + Clone,
+    {
+        let parsed_args = Args::parse_from(string_args);
+        let result = parsed_args.mushroom_from_args();
+        assert_eq!(
+            result,
+            mushroom::Mushroom {
+                stalk_h,
+                stalk_r,
+                cap_h,
+                cap_r,
+                cap_style,
+            }
+        );
+    }
+
+    #[test]
+    fn defaults() {
+        validate_mushroom_from_args(["prog"], 66.0, 5.0, 34.0, 50.0, mushroom::CapStyle::Dome);
+    }
+
+    #[test]
+    fn height_only() {
+        validate_mushroom_from_args(
+            ["prog", "--height", "200"],
+            132.0,
+            10.0,
+            68.0,
+            100.0,
+            mushroom::CapStyle::Dome,
+        );
+    }
+
+    #[test]
+    fn height_stalk_h() {
+        validate_mushroom_from_args(
+            ["prog", "--height", "200", "--stalk-h", "20"],
+            20.0,
+            10.0,
+            180.0,
+            100.0,
+            mushroom::CapStyle::Dome,
+        );
+    }
+
+    #[test]
+    fn height_cap_h() {
+        validate_mushroom_from_args(
+            ["prog", "--height", "200", "--cap-h", "20"],
+            180.0,
+            10.0,
+            20.0,
+            100.0,
+            mushroom::CapStyle::Dome,
+        );
+    }
+
+    #[test]
+    fn all() {
+        validate_mushroom_from_args(
+            [
+                "prog",
+                "--height",
+                "10",
+                "--stalk-h",
+                "20",
+                "--stalk-d",
+                "30",
+                "--cap-h",
+                "40",
+                "--cap-d",
+                "50",
+                "--cap-style",
+                "pointed",
+            ],
+            20.0,
+            15.0,
+            40.0,
+            25.0,
+            mushroom::CapStyle::Pointed,
+        );
+    }
+}
diff --git a/src/main.rs b/src/main.rs
index 5e0b998..83f0047 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,20 +1,19 @@
+pub mod args;
 pub mod layers;
 pub mod mushroom;
 pub mod render;
 pub mod translate;
 
-use self::mushroom::Mushroom;
-use clap::Parser;
 use std::fs::OpenOptions;
 
 extern crate approx;
-pub use serde_derive::{Deserialize, Serialize};
+use clap::Parser;
 
 fn main() {
-    let args = Args::parse();
+    let args = args::Args::parse();
 
     // Define the mushroom.
-    let mushroom = mushroom_from_args(&args);
+    let mushroom = args.mushroom_from_args();
 
     // Render the mushroom.
     // let mesh = render::cylinder(mushroom.stalk_h, mushroom.stalk_d, 128);
@@ -32,171 +31,3 @@ fn main() {
 
     println!("Generated from: {:?}", mushroom);
 }
-
-#[derive(Parser, Debug, Clone)]
-#[command(version, about, long_about = None)]
-struct Args {
-    /// File to save too.
-    #[arg(long, default_value = "mesh.stl")]
-    output: String,
-
-    /// Height of total mushroom in millimeters.
-    #[arg(long, default_value_t = 100)]
-    height: u32,
-
-    /// Stalk height in millimeters. Zero for default.
-    #[arg(long, default_value_t = 0)]
-    stalk_h: u32,
-
-    /// Stalk diameter in millimeters. Zero for default.
-    #[arg(long, default_value_t = 0)]
-    stalk_d: u32,
-
-    /// Cap height in millimeters. Zero for default.
-    #[arg(long, default_value_t = 0)]
-    cap_h: u32,
-
-    /// Stalk diameter in millimeters. Zero for default.
-    #[arg(long, default_value_t = 0)]
-    cap_d: u32,
-
-    /// Shape of the cap.
-    #[arg(long, default_value_t, value_enum)]
-    cap_style: mushroom::CapStyle,
-}
-
-fn mushroom_from_args(args: &Args) -> Mushroom {
-    // Default values are all based on height.
-    let stalk_h: f32 = if args.stalk_h != 0 {
-        args.stalk_h as f32
-    } else {
-        if args.cap_h != 0 {
-            (args.height - args.cap_h) as f32
-        } else {
-            args.height as f32 * 0.66
-        }
-    };
-    let stalk_r: f32 = if args.stalk_d != 0 {
-        args.stalk_d as f32
-    } else {
-        args.height as f32 / 10.
-    } / 2.0; // computer the diamter, and convert to radius.
-    let cap_h: f32 = if args.cap_h != 0 {
-        args.cap_h as f32
-    } else {
-        args.height as f32 - stalk_h
-    };
-    let cap_r: f32 = if args.cap_d != 0 {
-        args.cap_d as f32
-    } else {
-        args.height as f32
-    } / 2.0; // computer the diamter, and convert to radius.
-
-    let cap_style = args.cap_style.clone();
-
-    Mushroom {
-        stalk_h,
-        stalk_r,
-        cap_h,
-        cap_r,
-        cap_style,
-    }
-}
-
-#[cfg(test)]
-mod tests {
-    use super::*;
-    use std::ffi::OsString;
-
-    fn validate_mushroom_from_args<I, T>(
-        string_args: I,
-        stalk_h: f32,
-        stalk_r: f32,
-        cap_h: f32,
-        cap_r: f32,
-        cap_style: mushroom::CapStyle,
-    ) where
-        I: IntoIterator<Item = T>,
-        T: Into<OsString> + Clone,
-    {
-        let parsed_args = Args::parse_from(string_args);
-        let result = mushroom_from_args(&parsed_args);
-        assert_eq!(
-            result,
-            Mushroom {
-                stalk_h,
-                stalk_r,
-                cap_h,
-                cap_r,
-                cap_style,
-            }
-        );
-    }
-
-    #[test]
-    fn defaults() {
-        validate_mushroom_from_args(["prog"], 66.0, 5.0, 34.0, 50.0, mushroom::CapStyle::Dome);
-    }
-
-    #[test]
-    fn height_only() {
-        validate_mushroom_from_args(
-            ["prog", "--height", "200"],
-            132.0,
-            10.0,
-            68.0,
-            100.0,
-            mushroom::CapStyle::Dome,
-        );
-    }
-
-    #[test]
-    fn height_stalk_h() {
-        validate_mushroom_from_args(
-            ["prog", "--height", "200", "--stalk-h", "20"],
-            20.0,
-            10.0,
-            180.0,
-            100.0,
-            mushroom::CapStyle::Dome,
-        );
-    }
-
-    #[test]
-    fn height_cap_h() {
-        validate_mushroom_from_args(
-            ["prog", "--height", "200", "--cap-h", "20"],
-            180.0,
-            10.0,
-            20.0,
-            100.0,
-            mushroom::CapStyle::Dome,
-        );
-    }
-
-    #[test]
-    fn all() {
-        validate_mushroom_from_args(
-            [
-                "prog",
-                "--height",
-                "10",
-                "--stalk-h",
-                "20",
-                "--stalk-d",
-                "30",
-                "--cap-h",
-                "40",
-                "--cap-d",
-                "50",
-                "--cap-style",
-                "pointed",
-            ],
-            20.0,
-            15.0,
-            40.0,
-            25.0,
-            mushroom::CapStyle::Pointed,
-        );
-    }
-}