diff --git a/src/css.rs b/src/css.rs
new file mode 100644
index 0000000..b9dd41f
--- /dev/null
+++ b/src/css.rs
@@ -0,0 +1,94 @@
+//! # Convert from SCSS AST to CSS 
+use std::io;
+use crate::{Selector, Style, StyleSheet, Stmt, RuleSet};
+
+
+#[derive(Debug, Clone)]
+pub struct Block {
+    selector: Selector,
+    styles: Vec<Style>,
+}
+
+impl Block {
+    fn new(selector: Selector) -> Self {
+        Block {
+            selector,
+            styles: Vec::new(),
+        }
+    }
+
+    fn push(&mut self, s: Style) {
+        self.styles.push(s);
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct Css {
+    blocks: Vec<Block>,
+    idx: usize,
+}
+
+impl Css {
+    pub fn new() -> Self {
+        Css {
+            blocks: Vec::new(),
+            idx: 0,
+        }
+    }
+
+    pub fn from_stylesheet(s: StyleSheet) -> Self {
+        Css {
+            blocks: Vec::new(),
+            idx: 0,
+        }
+        .parse_stylesheet(s)
+    }
+
+    fn parse_stmt(&mut self, stmt: Stmt) {
+        match stmt {
+            Stmt::Style(s) => self.blocks[self.idx - 1].push(s),
+            Stmt::RuleSet(RuleSet {
+                selector,
+                super_selector,
+                rules,
+            }) => {
+                if self.idx == 0 {
+                    self.idx = self.blocks.len() + 1;
+                    self.blocks.push(Block::new(super_selector.zip(selector)));
+                    for rule in rules {
+                        self.parse_stmt(rule);
+                    }
+                    self.idx = 0;
+                } else {
+                    self.idx += 1;
+                    self.blocks.push(Block::new(super_selector.zip(selector)));
+                    for rule in rules {
+                        self.parse_stmt(rule);
+                    }
+                    self.idx -= 1;
+                }
+            }
+        }
+    }
+
+    fn parse_stylesheet(mut self, s: StyleSheet) -> Css {
+        for stmt in s.rules {
+            self.parse_stmt(stmt);
+        }
+        self
+    }
+
+    pub fn pretty_print<W: std::io::Write>(self, buf: &mut W) -> io::Result<()> {
+        for block in self.blocks {
+            if block.styles.is_empty() {
+                continue;
+            }
+            writeln!(buf, "{} {{", block.selector)?;
+            for style in block.styles {
+                writeln!(buf, "  {}", style)?;
+            }
+            writeln!(buf, "}}")?;
+        }
+        Ok(())
+    }
+}
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index b28f361..c98bd30 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -33,6 +33,7 @@ use std::{
 };
 
 use crate::common::{Keyword, Pos, Symbol, Whitespace};
+use crate::css::Css;
 use crate::format::PrettyPrinter;
 use crate::lexer::Lexer;
 use crate::selector::Selector;
@@ -40,6 +41,7 @@ use crate::units::Unit;
 
 mod color;
 mod common;
+mod css;
 mod error;
 mod format;
 mod lexer;
@@ -221,96 +223,6 @@ impl StyleSheet {
     }
 }
 
-#[derive(Debug, Clone)]
-pub struct Block {
-    selector: Selector,
-    styles: Vec<Style>,
-}
-
-impl Block {
-    fn new(selector: Selector) -> Self {
-        Block {
-            selector,
-            styles: Vec::new(),
-        }
-    }
-
-    fn push(&mut self, s: Style) {
-        self.styles.push(s);
-    }
-}
-
-#[derive(Debug, Clone)]
-pub struct Css {
-    blocks: Vec<Block>,
-    idx: usize,
-}
-
-impl Css {
-    pub fn new() -> Self {
-        Css {
-            blocks: Vec::new(),
-            idx: 0,
-        }
-    }
-
-    pub fn from_stylesheet(s: StyleSheet) -> Self {
-        Css {
-            blocks: Vec::new(),
-            idx: 0,
-        }
-        .parse_stylesheet(s)
-    }
-
-    fn parse_stmt(&mut self, stmt: Stmt) {
-        match stmt {
-            Stmt::Style(s) => self.blocks[self.idx - 1].push(s),
-            Stmt::RuleSet(RuleSet {
-                selector,
-                super_selector,
-                rules,
-            }) => {
-                if self.idx == 0 {
-                    self.idx = self.blocks.len() + 1;
-                    self.blocks.push(Block::new(super_selector.zip(selector)));
-                    for rule in rules {
-                        self.parse_stmt(rule);
-                    }
-                    self.idx = 0;
-                } else {
-                    self.idx += 1;
-                    self.blocks.push(Block::new(super_selector.zip(selector)));
-                    for rule in rules {
-                        self.parse_stmt(rule);
-                    }
-                    self.idx -= 1;
-                }
-            }
-        }
-    }
-
-    fn parse_stylesheet(mut self, s: StyleSheet) -> Css {
-        for stmt in s.rules {
-            self.parse_stmt(stmt);
-        }
-        self
-    }
-
-    pub fn pretty_print<W: std::io::Write>(self, buf: &mut W) -> io::Result<()> {
-        for block in self.blocks {
-            if block.styles.is_empty() {
-                continue;
-            }
-            writeln!(buf, "{} {{", block.selector)?;
-            for style in block.styles {
-                writeln!(buf, "  {}", style)?;
-            }
-            writeln!(buf, "}}")?;
-        }
-        Ok(())
-    }
-}
-
 #[derive(Debug, Clone)]
 struct StyleSheetParser<'a> {
     variables: HashMap<String, String>,