diff --git a/rustfmt.toml b/rustfmt.toml
new file mode 100644
index 0000000..2c4092d
--- /dev/null
+++ b/rustfmt.toml
@@ -0,0 +1,2 @@
+enum_discrim_align_threshold = 16
+struct_field_align_threshold = 16
diff --git a/src/syntax/ast.rs b/src/syntax/ast.rs
index e69de29..8a80787 100644
--- a/src/syntax/ast.rs
+++ b/src/syntax/ast.rs
@@ -0,0 +1,117 @@
+use lasso::Spur;
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct Span {
+    pub start: usize,
+    pub end:   usize,
+}
+
+impl From<std::ops::Range<usize>> for Span {
+    fn from(value: std::ops::Range<usize>) -> Self {
+        Self {
+            start: value.start,
+            end:   value.end,
+        }
+    }
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub struct Spanned<T> {
+    pub item: T,
+    pub span: Span,
+}
+
+impl<T> Spanned<T> {
+    #[inline]
+    pub fn new(item: T, span: impl Into<Span>) -> Self {
+        Self {
+            item,
+            span: span.into(),
+        }
+    }
+}
+
+pub type SpanExpr<'a> = Spanned<Expr<'a>>;
+pub type ExprRef<'a> = &'a SpanExpr<'a>;
+pub type ExprList<'a> = &'a [SpanExpr<'a>];
+pub type Ident = Spur;
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Expr<'a> {
+    Ident(Ident),
+    Path(ExprList<'a>),
+    Literal(Literal),
+    Call(ExprRef<'a>, ExprList<'a>),
+    Binary(Spanned<BinaryOp>, ExprRef<'a>, ExprRef<'a>),
+    Unary(Spanned<UnaryOp>, ExprRef<'a>),
+    Def {
+        kind:  DefKind,
+        ident: Spanned<Ident>,
+        ty:    Option<Spanned<Type>>,
+        init:  Option<ExprRef<'a>>,
+    },
+    Set(ExprRef<'a>, ExprRef<'a>),
+    Loop(ExprList<'a>),
+    Block(ExprList<'a>),
+    Switch {
+        on:       ExprRef<'a>,
+        branches: &'a [(Spanned<Switcher>, ExprRef<'a>)],
+        else_:    ExprRef<'a>,
+    },
+    CondSwitch {
+        branches: &'a [(ExprRef<'a>, ExprRef<'a>)],
+        else_:    ExprRef<'a>,
+    },
+    Func {
+        ident:  Spanned<Ident>,
+        params: &'a [(Spanned<Ident>, Spanned<Type>)],
+        ret:    Spanned<Type>,
+        body:   ExprList<'a>,
+    },
+    Break(Option<ExprRef<'a>>),
+    Return(Option<ExprRef<'a>>),
+    Continue,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Type {
+    Ident(Ident),
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Switcher {
+    Literal(Literal),
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum DefKind {
+    Const,
+    Var,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum Literal {
+    String(Spur),
+    Int(u64),
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum BinaryOp {
+    Plus,
+    Minus,
+    Star,
+    Slash,
+    Equ,
+    Neq,
+    Lt,
+    Gt,
+    LtEq,
+    GtEq,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq, Eq)]
+pub enum UnaryOp {
+    Minus,
+    Not,
+    Star,
+}
diff --git a/src/syntax/token.rs b/src/syntax/token.rs
index e165690..5f44839 100644
--- a/src/syntax/token.rs
+++ b/src/syntax/token.rs
@@ -47,6 +47,10 @@ pub enum Token {
     #[token("include")] Include,
     #[token("switch")] Switch,
     #[token("loop")] Loop,
+    #[token("return")] Return,
+    #[token("break")] Break,
+    #[token("continue")] Continue,
+    #[token("uninit")] Uninit,
     #[token("asm")] Asm,
 
     #[regex(