diff --git a/README.md b/README.md
index 5d56fe0..ed0942a 100644
--- a/README.md
+++ b/README.md
@@ -1,7 +1,7 @@
 # puyo 3 (this time it's nameful)
 
 ## semantics
-single-threaded, dynamically-typed (because lol), multiple named returns by default
+single-threaded, dynamically-typed (because lol), multiple named returns by default, pass-by-value
 
 functions take and return a map ALWAYS
 
diff --git a/src/ast.rs b/src/ast.rs
new file mode 100644
index 0000000..173d0f2
--- /dev/null
+++ b/src/ast.rs
@@ -0,0 +1,29 @@
+use crate::{map::Map, symbol::Symbol, val::Val};
+
+#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
+pub enum Ident {
+    /// `x`
+    Local(Symbol),
+    /// `^x`
+    Return(Symbol),
+}
+
+#[derive(Debug, Clone)]
+pub enum Ast {
+    /// `x`, `^x`
+    Var(Ident),
+    /// `x = y; => y`
+    Set(Ident, Box<Ast>),
+    /// fn ([a b] [c d]) ( ... )
+    Fn {
+        inputs: Vec<Symbol>,
+        outputs: Vec<Symbol>,
+        body: Vec<Ast>,
+    },
+    /// `{x, y: z}`
+    Map(Map<Ast>),
+    /// `f x`
+    App(Box<Ast>, Box<Ast>),
+    /// `x + y` (only builtins, sorry)
+    BinOp(Box<Ast>, fn(Val, Val) -> Val, Box<Ast>),
+}
diff --git a/src/main.rs b/src/main.rs
index e7a11a9..eff9d54 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,9 @@
+mod ast;
+mod map;
+mod parser;
+mod symbol;
+mod val;
+
 fn main() {
     println!("Hello, world!");
 }
diff --git a/src/map.rs b/src/map.rs
new file mode 100644
index 0000000..826a9dd
--- /dev/null
+++ b/src/map.rs
@@ -0,0 +1,5 @@
+use std::collections::HashMap;
+
+use crate::symbol::Symbol;
+
+pub type Map<V> = HashMap<Symbol, V>;
diff --git a/src/parser.rs b/src/parser.rs
new file mode 100644
index 0000000..e69de29
diff --git a/src/symbol.rs b/src/symbol.rs
new file mode 100644
index 0000000..33e0bd4
--- /dev/null
+++ b/src/symbol.rs
@@ -0,0 +1,2 @@
+// TODO: intern lol
+pub type Symbol = String;
diff --git a/src/val.rs b/src/val.rs
new file mode 100644
index 0000000..c478b95
--- /dev/null
+++ b/src/val.rs
@@ -0,0 +1,25 @@
+use std::fmt;
+
+use crate::{map::Map, symbol::Symbol};
+
+pub enum Val {
+    Number(f64),
+    Function {
+        inputs: Vec<Symbol>,
+        outputs: Vec<Symbol>,
+        run: Box<dyn FnMut(Map<Val>) -> Val>,
+    },
+    Map(Map<Val>),
+}
+
+impl fmt::Debug for Val {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::Number(n) => write!(f, "{n:?}"),
+            Self::Function {
+                inputs, outputs, ..
+            } => write!(f, "fn([{}], [{}]", inputs.join(" "), outputs.join(" ")),
+            Self::Map(map) => write!(f, "{map:?}"),
+        }
+    }
+}