diff --git a/.clang-format b/.clang-format
index 8e22be5..382a3e9 100644
--- a/.clang-format
+++ b/.clang-format
@@ -3,6 +3,7 @@ AlignAfterOpenBracket: AlwaysBreak
 AllowShortBlocksOnASingleLine: "Always"
 AlignConsecutiveShortCaseStatements:
   Enabled: true
+AllowShortCaseLabelsOnASingleLine: 'true'
 AllowShortEnumsOnASingleLine: 'false'
 AllowShortIfStatementsOnASingleLine: WithoutElse
 AllowShortLambdasOnASingleLine: 'true'
diff --git a/src/ast.h b/src/ast.h
new file mode 100644
index 0000000..41aec95
--- /dev/null
+++ b/src/ast.h
@@ -0,0 +1,198 @@
+#ifndef WINTER_AST_H
+#define WINTER_AST_H
+
+#include <optional>
+#include <string>
+#include <variant>
+#include <vector>
+
+#include "lexer.h"
+
+namespace Winter {
+
+    // pre-declarations
+    struct Expr;
+    struct aliasNode;
+    struct argNode;
+    struct assignNode;
+    struct binaryExpr;
+    struct blockNode;
+    struct classNode;
+    struct enumNode;
+    struct forEachStmt;
+    struct forStmt;
+    struct funcCallStmt;
+    struct funcNode;
+    struct ifStmt;
+    struct importNode;
+    struct interfaceNode;
+    struct letStmt;
+    struct methodCallStmt;
+    struct moduleNode;
+    struct retStmt;
+    struct tertiaryExpr;
+    struct typeDeclarationNode;
+    struct typeNode;
+    struct unaryExpr;
+    struct varDeclarationNode;
+
+    // variants
+    using Stmt_t = std::variant<forStmt, ifStmt, retStmt, funcCallStmt, methodCallStmt>;
+    using Expr_t = std::variant<binaryExpr, tertiaryExpr, unaryExpr>;
+    using ExprStmt_t = std::variant<Expr_t, Stmt_t>;
+    using Definitions_t = std::variant<letStmt, typeNode, aliasNode>;
+    using Declarations_t = std::variant<varDeclarationNode, typeDeclarationNode>;
+    using BlockItem_t = std::variant<Stmt_t, letStmt, assignNode, Expr_t, typeNode, aliasNode>;
+
+    // definitions
+
+    // ALIAS IDENT EQUAL IDENT SEMICOLON
+    // ALIAS IDENT EQUAL FUNC...
+    struct aliasNode {
+        std::string name;
+        std::string type;
+    };
+
+    // IDENT COLON IDENT
+    // name        type
+    struct argNode {
+        std::string name = "";
+        std::string type = "";
+    };
+
+    // IDENT EQUAL expr
+    struct assignNode {
+        std::string lhs = "";
+        Expr_t rhs;
+    };
+
+    struct binaryExpr {
+        Expr_t lhs;
+        TokenType symbol;
+        Expr_t rhs;
+    };
+
+    struct blockNode {
+        std::vector<BlockItem_t> items = {};
+    };
+
+    struct classNode {
+        std::optional<std::string> interfaceName;
+        std::vector<letStmt> attributes = {};
+        std::vector<letStmt> methods = {};
+    };
+
+    // ENUM LBRACE (IDENT COMMA) RBRACE
+    struct enumNode {
+        std::string enumNamespace;
+        std::vector<std::string> idents = {};
+    };
+
+    struct forStmt {
+        letStmt start;
+        assignNode stop;
+        unaryExpr step;
+        blockNode body;
+    };
+
+    // FOR LPAREN IDENT COLON IDENT RPAREN BLOCK
+    struct forEachStmt {
+        std::string element;
+        std::string container;
+    };
+
+    // IDENT LPAREN (IDENT|EXPR) SEMICOLON
+    struct funcCallStmt {
+        std::string ident;
+        std::vector<Expr_t> params;
+    };
+
+    // FUNC LPAREN (argNode...) RPAREN IDENT LBRACE blockNode RBRACE
+    struct funcNode {
+        std::vector<argNode> arguments = {};
+        std::string returnType;
+        blockNode block;
+    };
+
+    // IF LPAREN Expr_t RPAREN blockNode ELSE [block|IF]
+    struct ifStmt {
+        Expr_t expr;
+        blockNode ifBlock;
+        std::optional<blockNode> elseBlock;
+    };
+
+    // IMPORT IDENT
+    struct importNode {
+        std::string modName;
+    };
+
+    struct interfaceNode {
+        std::vector<Declarations_t> declarations = {};
+    };
+
+    // LET IDENT (COLON IDENT) EQUAL Expr_t SEMICOLON
+    // LET IDENT (LSQUACKET (IDENT COMMA) RSQUACKET) EQUAL [FUNC|IMPORT|CLASS|INTERFACE]
+    struct letStmt {
+        std::string name = "";
+        std::vector<std::string> generics = {};
+        std::optional<std::string> typeLiteral;
+        std::variant<funcNode, importNode> body;
+    };
+
+    struct methodCallStmt {
+        std::string objectName;
+        funcCallStmt methodCall;
+    };
+
+    // MOD, IDENT, SEMICOLON, [let|type {} ]
+    struct moduleNode {
+        std::string moduleName = "";
+        std::vector<Definitions_t> contents = {};
+    };
+
+    struct retStmt {
+        Expr_t expr;
+    };
+
+    // NOTE: Only tertiary expr is ?:
+    struct tertiaryExpr {
+        Expr_t left;
+        Expr_t middle;
+        Expr_t right;
+    };
+
+    // TYPE IDENT EQUAL [enum|class|interface]
+    struct typeNode {
+        std::string name = "";
+        std::vector<std::string> generics = {};
+        std::optional<std::string> typeLiteral;
+        std::variant<enumNode, classNode, interfaceNode> body;
+    };
+
+    // TYPE IDENT EQUAL ...
+    struct typeDeclarationNode {
+        std::string name;
+        TokenType type;  // func, enum, class
+
+        // func
+        std::optional<std::vector<argNode>> args;
+        std::optional<std::string> returnType;
+
+        // class implements interface
+        std::optional<std::string> interfaceName;
+    };
+
+    struct unaryExpr {
+        TokenType symbol;
+        Expr_t operand;
+    };
+
+    // LET IDENT COLON IDENT SEMI
+    struct varDeclarationNode {
+        std::string name;
+        std::optional<std::string> type;
+    };
+
+}  // namespace Winter
+
+#endif  // WINTER_AST_H
diff --git a/src/lexer.cpp b/src/lexer.cpp
index ad9b6ba..593afca 100644
--- a/src/lexer.cpp
+++ b/src/lexer.cpp
@@ -3,6 +3,7 @@
 #include <algorithm>
 #include <array>
 #include <format>
+#include <iterator>
 
 namespace Winter {
     auto Lexer::skipWhitespace() -> void {
@@ -11,6 +12,17 @@ namespace Winter {
         while (std::any_of(whitespace.begin(), whitespace.end(), cmp)) { playhead++; }
     }
 
+    auto Lexer::skipComment() -> void {
+        if (playhead >= src.size()) {
+            playhead = src.size();
+            return;
+        }
+
+        auto it = std::ranges::find_if(
+            src.begin() + playhead, src.end(), [](char c) { return c == '\n'; });
+        playhead = (it != src.end()) ? std::distance(src.begin(), it) : src.size();
+    }
+
     // TODO: utility?
     [[nodiscard]] auto between(int min, int max, int val) -> bool {
         return (min <= val && val <= max);
@@ -118,51 +130,34 @@ namespace Winter {
         src = source;
         skipWhitespace();
 
+        if (src.at(playhead) == '#') {
+            skipComment();
+            skipWhitespace();
+        }
+
         switch (src.at(playhead)) {
-            case '(':
-                return lexSingle(TokenType::LPAREN);
-            case ')':
-                return lexSingle(TokenType::RPAREN);
-            case '{':
-                return lexSingle(TokenType::LBRACE);
-            case '}':
-                return lexSingle(TokenType::RBRACE);
-            case '[':
-                return lexSingle(TokenType::LSQUACKET);
-            case ']':
-                return lexSingle(TokenType::RSQUACKET);
-            case ':':
-                return lexSingle(TokenType::COLON);
-            case ';':
-                return lexSingle(TokenType::SEMICOLON);
-            case '+':
-                return lexSingle(TokenType::PLUS);
-            case '-':
-                return lexSingle(TokenType::MINUS);
-            case '*':
-                return lexSingle(TokenType::STAR);
-            case '/':
-                return lexSingle(TokenType::SLASH);
-            case ',':
-                return lexSingle(TokenType::COMMA);
-            case '.':
-                return lexDouble('.', TokenType::DOT, TokenType::DOT_DOT);
-            case '>':
-                return lexDouble('=', TokenType::GREATER, TokenType::GREATER_EQ);
-            case '<':
-                return lexDouble('=', TokenType::LESS, TokenType::LESS_EQ);
-            case '!':
-                return lexDouble('=', TokenType::NOT, TokenType::NOT_EQ);
-            case '&':
-                return lexDouble('&', TokenType::ERROR, TokenType::AND);
-            case '|':
-                return lexDouble('|', TokenType::ERROR, TokenType::OR);
-            case '\'':
-                return lexChar();
-            case '"':
-                return lexString();
-            default:
-                break;
+            case '(':  return lexSingle(TokenType::LPAREN);
+            case ')':  return lexSingle(TokenType::RPAREN);
+            case '{':  return lexSingle(TokenType::LBRACE);
+            case '}':  return lexSingle(TokenType::RBRACE);
+            case '[':  return lexSingle(TokenType::LSQUACKET);
+            case ']':  return lexSingle(TokenType::RSQUACKET);
+            case ':':  return lexSingle(TokenType::COLON);
+            case ';':  return lexSingle(TokenType::SEMICOLON);
+            case '+':  return lexDouble('+', TokenType::PLUS, TokenType::PLUS_PLUS);
+            case '-':  return lexDouble('-', TokenType::MINUS, TokenType::MINUS_MINUS);
+            case '*':  return lexSingle(TokenType::STAR);
+            case '/':  return lexSingle(TokenType::SLASH);
+            case ',':  return lexSingle(TokenType::COMMA);
+            case '.':  return lexDouble('.', TokenType::DOT, TokenType::DOT_DOT);
+            case '>':  return lexDouble('=', TokenType::GREATER, TokenType::GREATER_EQ);
+            case '<':  return lexDouble('=', TokenType::LESS, TokenType::LESS_EQ);
+            case '!':  return lexDouble('=', TokenType::NOT, TokenType::NOT_EQ);
+            case '&':  return lexDouble('&', TokenType::ERROR, TokenType::AND);
+            case '|':  return lexDouble('|', TokenType::ERROR, TokenType::OR);
+            case '\'': return lexChar();
+            case '"':  return lexString();
+            default:   break;
         }
 
         if (isNumeric()) { return lexNumeric(); }
diff --git a/src/lexer.h b/src/lexer.h
index 12ff349..d8af12c 100644
--- a/src/lexer.h
+++ b/src/lexer.h
@@ -24,7 +24,9 @@ namespace Winter {
         COLON,
         SEMICOLON,
         PLUS,
+        PLUS_PLUS,
         MINUS,
+        MINUS_MINUS,
         STAR,
         SLASH,
         COMMA,
@@ -47,8 +49,10 @@ namespace Winter {
 
         // KEYWORDS
         ALIAS,
+        BREAK,
         CASE,
         CLASS,
+        CONTINUE,
         DEFAULT,
         ENUM,
         FALSE,
@@ -91,6 +95,8 @@ namespace Winter {
 
         const std::unordered_map<std::string_view, TokenType> keywords = {
             {"alias"sv, TokenType::ALIAS},
+            {"break"sv, TokenType::BREAK},
+            {"continue"sv, TokenType::CONTINUE},
             {"case"sv, TokenType::CASE},
             {"class"sv, TokenType::CLASS},
             {"default"sv, TokenType::DEFAULT},
@@ -111,6 +117,7 @@ namespace Winter {
 
         explicit Lexer() {}
         auto skipWhitespace() -> void;
+        auto skipComment() -> void;
         [[nodiscard]] auto isNumeric() -> bool;
         [[nodiscard]] auto isLetter() -> bool;
         [[nodiscard]] auto lexNumeric() -> token_result_t;
diff --git a/tests/lexer_test.h b/tests/lexer_test.h
index 69645fc..a2a2590 100644
--- a/tests/lexer_test.h
+++ b/tests/lexer_test.h
@@ -20,6 +20,25 @@ constexpr auto test_skipWhitespace([[maybe_unused]] Willow::Test* test) -> int {
     return 0;
 }
 
+constexpr auto test_skipComment([[maybe_unused]] Willow::Test* test) -> int {
+    auto L = Winter::Lexer();
+    L.src = "# this is a comment\n  0"sv;
+    L.skipComment();
+
+    if (L.playhead != 19) {
+        test->alert("Playhead = " + std::to_string(L.playhead));
+        return 1;
+    }
+
+    L.skipWhitespace();
+    if (L.playhead != 22) {
+        test->alert("Playhead = " + std::to_string(L.playhead));
+        return 2;
+    }
+
+    return 0;
+}
+
 constexpr auto test_between([[maybe_unused]] Willow::Test* test) -> int {
     if (!Winter::between(1, 10, 5)) { return 1; }
     if (Winter::between(1, 10, 20)) { return 2; }
diff --git a/tests/test.cpp b/tests/test.cpp
index bbbcd07..5daa790 100644
--- a/tests/test.cpp
+++ b/tests/test.cpp
@@ -9,6 +9,7 @@ auto main(int argc, char* argv[]) -> int {
     Willow::registerTests({
         // lexer_test.h
         {"skipWhitespace", test_skipWhitespace},
+        {"skipComment", test_skipComment},
         {"between", test_between},
         {"isNumeric", test_isNumeric},
         {"isLetter", test_isLetter},