diff --git a/src/ast.rs b/src/ast.rs
new file mode 100644
index 00000000..434a246a
--- /dev/null
+++ b/src/ast.rs
@@ -0,0 +1,94 @@
+use crate::variables::Value;
+
+type Span = std::ops::Range<usize>;
+
+#[derive(Debug)]
+pub struct Iden(String);
+
+#[derive(Debug)]
+pub struct Block {
+    pub block: Vec<Stmt>,
+}
+
+/// A syntactic unit expressing an effect.
+#[derive(Debug)]
+pub struct Stmt {
+    pub kind: StmtKind,
+    pub span: Span,
+}
+
+#[derive(Debug)]
+pub enum StmtKind {
+    // Control flow
+    If {
+        cond: Expr,
+        body: Block,
+    },
+    Loop {
+        body: Block,
+    },
+    Break,
+    HopBack,
+
+    Var {
+        iden: Iden,
+        init: Option<Expr>,
+    },
+
+    Functio {
+        iden: Iden,
+        args: Vec<Iden>,
+        body: Block,
+    },
+    Call {
+        iden: Iden,
+        args: Vec<Expr>,
+    },
+    Print(Expr),
+    Melo(Iden),
+}
+
+impl Stmt {
+    pub fn new(kind: StmtKind, span: Span) -> Self {
+        Self { kind, span }
+    }
+}
+
+/// Expression is parse unit which do not cause any effect,
+/// like math and logical operations or values.
+#[derive(Debug)]
+pub struct Expr {
+    kind: ExprKind,
+    span: Span,
+}
+
+#[derive(Debug)]
+pub enum ExprKind {
+    Binary {
+        lhs: Box<Expr>,
+        rhs: Box<Expr>,
+        kind: BinOpKind,
+    },
+    Not(Box<Expr>),
+    Literal(Value),
+}
+
+impl Expr {
+    pub fn new(kind: ExprKind, span: Span) -> Self {
+        Self { kind, span }
+    }
+}
+
+#[derive(Debug)]
+pub enum BinOpKind {
+    Add,
+    Subtract,
+    Multiply,
+    Divide,
+    Greater,
+    Less,
+    Equal,
+    NotEqual,
+    And,
+    Or,
+}