diff --git a/src/lexer.ts b/src/lexer.ts
index a5ff034..73261b0 100644
--- a/src/lexer.ts
+++ b/src/lexer.ts
@@ -1,135 +1,161 @@
 export type Token =
-    | { kind: 'let' }
-    | { kind: 'in' }
-
-    | { kind: 'number', value: number }
+    // Literals
+    | { kind: 'int', value: number }
+    | { kind: 'float', value: number }
+    | { kind: 'string', value: string }
     | { kind: 'ident', value: string }
+    | { kind: 'type-ident', value: string }
 
-    | { kind: 'equals' }
-
+    // Brackets
     | { kind: 'open-paren' }
     | { kind: 'close-paren' }
+    | { kind: 'open-brace' }
+    | { kind: 'close-brace' }
+    | { kind: 'open-bracket' }
+    | { kind: 'close-bracket' }
 
+    // Symbols
+    | { kind: 'equals' }
+    | { kind: 'colon' }
+    | { kind: 'backslash' }
+    | { kind: 'pipe' }
+    | { kind: 'greater-than' }
     | { kind: 'comma' }
-    | { kind: 'arrow' }
-
-    | { kind: 'if' }
-    | { kind: 'then' }
-    | { kind: 'else' }
-
-    | { kind: 'true' }
-    | { kind: 'false' }
+    | { kind: 'ampersand' }
+    | { kind: 'underscore' }
+    | { kind: 'dot' }
+    | { kind: 'at' }
 
+    // Anithmetic
     | { kind: 'plus' }
     | { kind: 'minus' }
     | { kind: 'star' }
     | { kind: 'slash' }
-    | { kind: 'less-than' }
-    | { kind: 'greater-than' }
-    | { kind: 'double-equals' }
+
+    | { kind: 'eof' }
 
 export function tokenize(source: string): Token[] {
-    const tokens = [];
+    const tokens: Token[] = [];
 
     let i = 0;
     while (i < source.length) {
         const char = source[i];
 
-        // skip whitespace
+        // Whitespace
         if (/\s/.test(char)) {
             i++;
             continue;
         }
 
-        // Multi-char: numbers
-        if (/[0-9]/.test(char)) {
-            let num = '';
-            while (i < source.length && /[0-9]/.test(source[i])) {
-                num += source[i];
+        if (char === '#') {
+            while (i < source.length && source[i] !== '\n') {
                 i++;
             }
-            tokens.push({ kind: 'number', value: parseInt(num) });
             continue;
         }
 
-        // Multi-char: equals
-        if (char === '=') {
-            const nextChar = source[i + 1];
+        // Numbers
+        if (/[0-9]/.test(char)) { // have to start with a digit (?)
+            let num = '';
+            let hasDot = false;
 
-            if (nextChar === '=') {
-                tokens.push({ kind: 'double-equals' });
-                i++;
-                continue;
-            } else if (nextChar === '>') {
-                tokens.push({ kind: 'arrow' });
-                i++;
-                continue;
-            } else {
-                tokens.push({ kind: 'equals' });
+            while (i < source.length && /[0-9.]/.test(source[i])) {
+                if (source[i] === '.') {
+                    if (hasDot) break;
+                    hasDot = true;
+                }
+                num += source[i];
                 i++;
-                continue;
             }
+
+            tokens.push(hasDot
+                ? { kind: 'float', value: parseFloat(num) }
+                : { kind: 'int', value: parseInt(num) });
+
+            continue;
         }
 
-        // Multi-char: strings
-        if (/[A-Za-z]/.test(char)) {
+        // Idents
+        if (/[A-Za-z_]/.test(char)) {
             let str = '';
-            while (i < source.length && /[A-Za-z]/.test(source[i])) {
+            while (i < source.length && /[A-Za-z0-9_!-]/.test(source[i])) {
                 str += source[i];
                 i++;
             }
 
-            if (str === 'let') {
-                tokens.push({ kind: 'let' });
-            } else if (str === 'in') {
-                tokens.push({ kind: 'in' });
-            } else if (str === 'if') {
-                tokens.push({ kind: 'if' });
-            } else if (str === 'then') {
-                tokens.push({ kind: 'then' });
-            } else if (str === 'else') {
-                tokens.push({ kind: 'else' });
-            } else if (str === 'true') {
-                tokens.push({ kind: 'true' });
-            } else if (str === 'false') {
-                tokens.push({ kind: 'false' });
-            } else {
-                tokens.push({ kind: 'ident', value: str });
-            }
+            const isType = /[A-Z]/.test(str[0]);
+
+            tokens.push(isType
+                ? { kind: 'type-ident', value: str }
+                : { kind: 'ident', value: str });
 
             continue;
         }
 
-        // TODO: floats
+        // Strings
+        if (char === '"') {
+            i++;
+            let str = '';
+
+            while (i < source.length && source[i] !== '"') {
+                if (source[i] === '\\') {
+                    i++;
+
+                    if (i >= source.length) {
+                        throw new Error('Unterminated string');
+                    }
+
+                    switch(source[i]) {
+                        case 'n': str += '\n'; break;
+                        case '"': str += '"'; break;
+                        case '\\': str += '\\'; break;
+                        case 't': str += '\t'; break;
+                    }
+                } else {
+                    str += source[i];
+                }
+
+                i++;
+            }
+
+            if (i >= source.length) {
+                throw new Error('Unterminated string');
+            }
+
+            tokens.push({ kind: 'string', value: str });
+
+            i++;
+
+            continue;
+        }
 
         switch (char) {
-            case ',':
-                tokens.push({ kind: 'comma' });
-                break;
-            case '+':
-                tokens.push({ kind: 'plus' });
-                break;
-            case '-':
-                tokens.push({ kind: 'minus' });
-                break;
-            case '*':
-                tokens.push({ kind: 'star' });
-                break;
-            case '/':
-                tokens.push({ kind: 'slash' });
-                break;
-            case '(':
-                tokens.push({ kind: 'open-paren' });
-                break;
-            case ')':
-                tokens.push({ kind: 'close-paren' });
-                break;
-            case '<':
-                tokens.push({ kind: 'less-than' });
-                break;
-            case '>':
-                tokens.push({ kind: 'greater-than' });
-                break;
+            // Brackets
+            case '(': tokens.push({ kind: 'open-paren' }); break;
+            case ')': tokens.push({ kind: 'close-paren' }); break;
+            case '{': tokens.push({ kind: 'open-brace' }); break;
+            case '}': tokens.push({ kind: 'close-brace' }); break;
+            case '[': tokens.push({ kind: 'open-bracket' }); break;
+            case ']': tokens.push({ kind: 'close-bracket' }); break;
+
+            // Symbols
+            case '=': tokens.push({ kind: 'equals' }); break;
+            case ':': tokens.push({ kind: 'colon' }); break;
+            case '\\': tokens.push({ kind: 'backslash' }); break;
+            case '|': tokens.push({ kind: 'pipe' }); break;
+            // case '<': tokens.push({ kind: 'less-than' }); break;
+            case '>': tokens.push({ kind: 'greater-than' }); break;
+            case ',': tokens.push({ kind: 'comma' }); break;
+            case '&': tokens.push({ kind: 'ampersand' }); break;
+            case '_': tokens.push({ kind: 'underscore' }); break;
+            case '.': tokens.push({ kind: 'dot' }); break;
+            case '@': tokens.push({ kind: 'at' }); break;
+
+            // Arithmetic
+            case '+': tokens.push({ kind: 'plus' }); break;
+            case '-': tokens.push({ kind: 'minus' }); break;
+            case '*': tokens.push({ kind: 'star' }); break;
+            case '/': tokens.push({ kind: 'slash' }); break;
         }
 
         i++;
diff --git a/src/main.ts b/src/main.ts
index 0c54a72..08f3329 100644
--- a/src/main.ts
+++ b/src/main.ts
@@ -2,6 +2,7 @@ import { evaluate } from './interpreter'
 import type { AST } from './ast'
 import type { Env } from './env'
 import { tokenize } from './lexer'
+import { Parser } from './parser'
 
 const ast: AST = {
     kind: 'binaryop',
@@ -26,52 +27,28 @@ const ast: AST = {
 
 const env: Env = new Map();
 
-const res = evaluate(ast, env);
-
-console.log(res);
-
-const ast2: AST = {
-    kind: 'let',
-    name: 'add',
-    value: {
-        kind: 'lambda',
-        params: ['x', 'y'],
-        body: {
-            kind: 'binaryop',
-            operator: '+',
-            left: {
-                kind: 'variable',
-                name: 'x',
-            },
-            right: {
-                kind: 'variable',
-                name: 'y',
-            }
-        }
-    },
-    body: {
-        kind: 'apply',
-        func: {
-            kind: 'variable',
-            name: 'add'
-        },
-        args: [
-            {
-                kind: 'literal',
-                value: { kind: 'int', value: 2 }
-            },
-            {
-                kind: 'literal',
-                value: { kind: 'int', value: 3 }
-            },
-        ]
-    }
-};
-
-const env2: Env = new Map();
-
-const res2 = evaluate(ast2, env2);
-
-console.log(res2);
-
-console.log(tokenize("let x = 5"));
+// const res = evaluate(ast, env);
+
+// console.log(res);
+
+const str = `
+# This is a comment
+double = x \\ x * 2
+read_line! : Unit \\ String
+`;
+console.log(tokenize(str));
+
+// const tokens = tokenize("x");
+// const p = new Parser(tokens);
+// console.log(p.parse());
+
+/*
+const tokens2 = tokenize("let x = (y) => 5 + y in x(3)");
+// const tokens2 = tokenize("let x = 5 in x * 4");
+// const tokens2 = tokenize("(x, y) => x + y");
+const p2 = new Parser(tokens2);
+const ast3 = p2.parse();
+const env3: Env = new Map();
+console.log(ast3);
+console.log(evaluate(ast3, env3));
+*/
diff --git a/src/parser.ts b/src/parser.ts
new file mode 100644
index 0000000..df16e4f
--- /dev/null
+++ b/src/parser.ts
@@ -0,0 +1,177 @@
+import type { Token } from './lexer'
+import type { AST } from './ast'
+
+export class Parser {
+    private tokens: Token[]
+    private pos: number = 0
+
+    constructor(tokens: Token[]) {
+        this.tokens = tokens;
+        console.log("tokens", tokens);
+    }
+
+    private current(): Token {
+        if (this.pos >= this.tokens.length) {
+            return { kind: 'eof' } as Token;
+        }
+        return this.tokens[this.pos];
+    }
+
+    private advance(): Token {
+        return this.tokens[this.pos++];
+    }
+
+    parse(): AST {
+        return this.parseExpression();
+    }
+
+    private parseExpression(): AST {
+        if (this.current().kind === 'let') {
+            return this.parseLet();
+        }
+        return this.parseAdditive();
+    }
+
+    private parsePrimary(): AST {
+        const token = this.current();
+
+        if (token.kind === 'open-paren') {
+            const savedPos = this.pos;
+            this.advance();
+
+            let isLambda = false;
+            if (this.current().kind === 'close-paren') {
+                isLambda = true;
+            } else if (this.current().kind === 'ident') {
+                let tempPos = this.pos;
+                this.advance();
+                if (this.current().kind === 'comma' || (this.current().kind === 'close-paren' && this.tokens[this.pos + 1]?.kind === 'arrow')) {
+                    isLambda = true;
+                }
+                this.pos = tempPos;
+            }
+
+            this.pos = savedPos;
+
+            if (isLambda) {
+                return this.parseLambda();
+            }
+
+            this.advance();
+            const expr = this.parseExpression();
+            this.expect('close-paren');
+            return expr;
+        }
+
+        if (token.kind === 'number') {
+            this.advance();
+
+            return { kind: 'literal', value: { kind: 'int', value: token.value } };
+        }
+
+        if (token.kind === 'ident') {
+            this.advance();
+
+            return { kind: 'variable', name: token.value };
+        }
+
+        throw new Error(`Unexpected token: ${token.kind}`);
+    }
+
+    private parseMultiplicative(): AST {
+        let left = this.parsePostfix();
+
+        while (this.current().kind === 'star' || this.current().kind === 'slash') {
+            const op = this.current().kind === 'star' ? '*' : '/';
+            this.advance();
+            const right = this.parsePostfix();
+
+            left = { kind: 'binaryop', operator: op, left, right };
+        }
+
+        return left;
+    }
+
+    private parseAdditive(): AST {
+        let left = this.parseMultiplicative();
+
+        while (this.current().kind === 'plus' || this.current().kind === 'minus') {
+            const op = this.current().kind === 'plus' ? '+' : '-';
+            this.advance();
+            const right = this.parseMultiplicative();
+
+            left = { kind: 'binaryop', operator: op, left, right };
+        }
+
+        return left;
+    }
+
+    private parseLet(): AST {
+        this.expect('let');
+        const nameToken = this.expect('ident');
+        const name = (nameToken as { value: string }).value;
+        this.expect('equals');
+        const value = this.parseExpression();
+        this.expect('in');
+        const body = this.parseExpression();
+
+        return { kind: 'let', name, value, body };
+    }
+
+    private parseLambda(): AST {
+        this.expect('open-paren');
+
+        const params: string[] = [];
+
+        if (this.current().kind !== 'close-paren') {
+            const first = this.expect('ident');
+            params.push((first as { value: string }).value);
+
+            while (this.current().kind === 'comma') {
+                this.advance();
+                const param = this.expect('ident');
+                params.push((param as { value: string }).value);
+            }
+        }
+
+        this.expect('close-paren');
+        this.expect('arrow');
+
+        const body = this.parseExpression();
+
+        return { kind: 'lambda', params, body }
+    }
+
+    private parsePostfix(): AST {
+        let expr = this.parsePrimary();
+
+        while (this.current().kind === 'open-paren') {
+            this.advance();
+
+            const args: AST[] = [];
+            if (this.current().kind !== 'close-paren') {
+                args.push(this.parseExpression());
+
+                while (this.current().kind === 'comma') {
+                    this.advance();
+                    args.push(this.parseExpression());
+                }
+            }
+
+            this.expect('close-paren');
+
+            expr = { kind: 'apply', func: expr, args };
+        }
+
+        return expr;
+    }
+
+    private expect(kind: Token['kind']): Token {
+        const token = this.current();
+        if (token.kind !== kind) {
+            throw new Error(`Expected ${kind}, got ${token.kind}`);
+        }
+
+        return this.advance();
+    }
+}