diff --git a/.clang-format b/.clang-format
new file mode 100644
index 0000000..af281a7
--- /dev/null
+++ b/.clang-format
@@ -0,0 +1,9 @@
+BasedOnStyle: WebKit
+IndentWidth: 4
+ColumnLimit: 80
+IndentCaseLabels: true
+BreakBeforeBraces: Custom
+BraceWrapping:
+    AfterFunction: true
+    SplitEmptyFunction: false
+
diff --git a/lexer.c b/lexer.c
index 9ec7c34..fcbdfc6 100644
--- a/lexer.c
+++ b/lexer.c
@@ -5,8 +5,9 @@
 #include <stdlib.h>
 #include <string.h>
 
-#define ASSERT_EXHAUSTIVE_MATCH()                                                                  \
-    (fprintf(stderr, "unexhaustive match at %s:%d in %s()\n", __FILE__, __LINE__, __func__),       \
+#define ASSERT_EXHAUSTIVE_MATCH()                                              \
+    (fprintf(stderr, "unexhaustive match at %s:%d in %s()\n", __FILE__,        \
+         __LINE__, __func__),                                                  \
         exit(1))
 
 Token lexer_skip_whitespace(Lexer* lexer);
@@ -19,10 +20,12 @@ Token lexer_make_char(Lexer* lexer);
 Token lexer_make_string(Lexer* lexer);
 void lexer_skip_literal_char(Lexer* lexer);
 Token lexer_make_single_char_token(Lexer* lexer, TokenType type);
+Token lexer_make_dot_token(Lexer* lexer);
+Token lexer_make_colon_token(Lexer* lexer);
 Token lexer_make_slash_token(Lexer* lexer);
 Token lexer_skip_singleline_comment(Lexer* lexer);
-Token lexer_make_single_or_double_char_token(
-    Lexer* lexer, TokenType single_type, char second_char, TokenType double_type);
+Token lexer_make_single_or_double_char_token(Lexer* lexer,
+    TokenType single_type, char second_char, TokenType double_type);
 Token lexer_skip_multiline_comment(Lexer* lexer);
 Token lexer_make_invalid_char(Lexer* lexer);
 Position lexer_position(const Lexer* lexer);
@@ -72,9 +75,14 @@ Token lexer_make_int_or_float(Lexer* lexer)
         lexer_step(lexer);
     if (!lexer_done(lexer) && lexer_current(lexer) == '.') {
         lexer_step(lexer);
-        while (!lexer_done(lexer) && isdigit(lexer_current(lexer)))
+        if (!lexer_done(lexer) && lexer_current(lexer) == '.') {
             lexer_step(lexer);
-        return lexer_token(lexer, TokenTypeFloat, begin);
+            return lexer_token(lexer, TokenTypeIntDoubleDot, begin);
+        } else {
+            while (!lexer_done(lexer) && isdigit(lexer_current(lexer)))
+                lexer_step(lexer);
+            return lexer_token(lexer, TokenTypeFloat, begin);
+        }
     } else {
         return lexer_token(lexer, TokenTypeInt, begin);
     }
@@ -125,6 +133,10 @@ Token lexer_make_id(Lexer* lexer)
         return lexer_token(lexer, TokenTypeFn, begin);
     else if (lexer_span_matches(lexer, begin, "return"))
         return lexer_token(lexer, TokenTypeReturn, begin);
+    else if (lexer_span_matches(lexer, begin, "mut"))
+        return lexer_token(lexer, TokenTypeMut, begin);
+    else if (lexer_span_matches(lexer, begin, "defer"))
+        return lexer_token(lexer, TokenTypeDefer, begin);
     else
         return lexer_token(lexer, TokenTypeId, begin);
 }
@@ -159,12 +171,11 @@ Token lexer_make_static_token(Lexer* lexer)
         case ']':
             return lexer_make_single_char_token(lexer, TokenTypeRBracket);
         case '.':
-            return lexer_make_single_or_double_char_token(
-                lexer, TokenTypeDot, '.', TokenTypeDoubleDot);
+            return lexer_make_dot_token(lexer);
         case ',':
             return lexer_make_single_char_token(lexer, TokenTypeComma);
         case ':':
-            return lexer_make_single_char_token(lexer, TokenTypeColon);
+            return lexer_make_colon_token(lexer);
         case ';':
             return lexer_make_single_char_token(lexer, TokenTypeSemicolon);
         case '&':
@@ -209,16 +220,21 @@ Token lexer_make_int_hex_binary_or_float(Lexer* lexer)
         while (!lexer_done(lexer) && isdigit(lexer_current(lexer)))
             lexer_step(lexer);
         return lexer_token(lexer, TokenTypeFloat, begin);
-    } else if (!lexer_done(lexer) && (lexer_current(lexer) == 'x' || lexer_current(lexer) == 'X')) {
+    } else if (!lexer_done(lexer)
+        && (lexer_current(lexer) == 'x' || lexer_current(lexer) == 'X')) {
+        lexer_step(lexer);
         while (!lexer_done(lexer)
             && (isdigit(lexer_current(lexer))
                 || (lexer_current(lexer) >= 'a' && lexer_current(lexer) <= 'f')
-                || (lexer_current(lexer) >= 'A' && lexer_current(lexer) <= 'F')))
+                || (lexer_current(lexer) >= 'A'
+                    && lexer_current(lexer) <= 'F')))
             lexer_step(lexer);
         return lexer_token(lexer, TokenTypeHex, begin);
-    } else if (!lexer_done(lexer) && (lexer_current(lexer) == 'b' || lexer_current(lexer) == 'B')) {
+    } else if (!lexer_done(lexer)
+        && (lexer_current(lexer) == 'b' || lexer_current(lexer) == 'B')) {
         lexer_step(lexer);
-        while (!lexer_done(lexer) && (lexer_current(lexer) == '0' || lexer_current(lexer) == '1'))
+        while (!lexer_done(lexer)
+            && (lexer_current(lexer) == '0' || lexer_current(lexer) == '1'))
             lexer_step(lexer);
         return lexer_token(lexer, TokenTypeBinary, begin);
     } else {
@@ -271,7 +287,8 @@ void lexer_skip_literal_char(Lexer* lexer)
         while (!lexer_done(lexer)
             && (isdigit(lexer_current(lexer))
                 || (lexer_current(lexer) >= 'a' && lexer_current(lexer) <= 'f')
-                || (lexer_current(lexer) >= 'A' && lexer_current(lexer) <= 'F')))
+                || (lexer_current(lexer) >= 'A'
+                    && lexer_current(lexer) <= 'F')))
             lexer_step(lexer);
     }
 }
@@ -283,8 +300,8 @@ Token lexer_make_single_char_token(Lexer* lexer, TokenType type)
     return lexer_token(lexer, type, begin);
 }
 
-Token lexer_make_single_or_double_char_token(
-    Lexer* lexer, TokenType single_type, char second_char, TokenType double_type)
+Token lexer_make_single_or_double_char_token(Lexer* lexer,
+    TokenType single_type, char second_char, TokenType double_type)
 {
     Position begin = lexer_position(lexer);
     lexer_step(lexer);
@@ -296,6 +313,48 @@ Token lexer_make_single_or_double_char_token(
     }
 }
 
+Token lexer_make_dot_token(Lexer* lexer)
+{
+    Position begin = lexer_position(lexer);
+    lexer_step(lexer);
+    if (!lexer_done(lexer) && lexer_current(lexer) == '.') {
+        lexer_step(lexer);
+        if (!lexer_done(lexer) && lexer_current(lexer) == '=') {
+            lexer_step(lexer);
+            return lexer_token(lexer, TokenTypeDoubleDotEqual, begin);
+        } else if (!lexer_done(lexer) && lexer_current(lexer) == '<') {
+            lexer_step(lexer);
+            return lexer_token(lexer, TokenTypeDoubleDotLt, begin);
+        } else {
+            return lexer_token(lexer, TokenTypeDoubleDot, begin);
+        }
+    } else if (!lexer_done(lexer) && isdigit(lexer_current(lexer))) {
+        lexer_step(lexer);
+        while (!lexer_done(lexer) && isdigit(lexer_current(lexer)))
+            lexer_step(lexer);
+        return lexer_token(lexer, TokenTypeFloat, begin);
+    } else {
+        return lexer_token(lexer, TokenTypeDot, begin);
+    }
+}
+
+Token lexer_make_colon_token(Lexer* lexer)
+{
+    Position begin = lexer_position(lexer);
+    lexer_step(lexer);
+    if (!lexer_done(lexer) && lexer_current(lexer) == ':') {
+        lexer_step(lexer);
+        if (!lexer_done(lexer) && lexer_current(lexer) == '<') {
+            lexer_step(lexer);
+            return lexer_token(lexer, TokenTypeDoubleColonLt, begin);
+        } else {
+            return lexer_token(lexer, TokenTypeDoubleColon, begin);
+        }
+    } else {
+        return lexer_token(lexer, TokenTypeColon, begin);
+    }
+}
+
 Token lexer_make_slash_token(Lexer* lexer)
 {
     Position begin = lexer_position(lexer);
@@ -343,9 +402,9 @@ Token lexer_skip_multiline_comment(Lexer* lexer)
         }
         lexer_step(lexer);
     }
-    return depth != 0
-        ? lexer_token(lexer, TokenTypeMalformedMultilineComment, lexer_position(lexer))
-        : lexer_next(lexer);
+    return depth != 0 ? lexer_token(
+               lexer, TokenTypeMalformedMultilineComment, lexer_position(lexer))
+                      : lexer_next(lexer);
 }
 
 Token lexer_make_invalid_char(Lexer* lexer)
@@ -417,93 +476,137 @@ const char* token_type_to_string(TokenType type)
 {
     switch (type) {
         case TokenTypeEof:
-            return "Eof";
+            return "TokenTypeEof";
         case TokenTypeInvalidChar:
-            return "InvalidChar";
+            return "TokenTypeInvalidChar";
         case TokenTypeMalformedMultilineComment:
-            return "MalformedMultilineComment";
+            return "TokenTypeMalformedMultilineComment";
         case TokenTypeMalformedChar:
-            return "MalformedChar";
+            return "TokenTypeMalformedChar";
         case TokenTypeMalformedString:
-            return "MalformedString";
+            return "TokenTypeMalformedString";
         case TokenTypeId:
-            return "Id";
+            return "TokenTypeId";
         case TokenTypeInt:
-            return "Int";
+            return "TokenTypeInt";
+        case TokenTypeIntDoubleDot:
+            return "TokenTypeIntDoubleDot";
         case TokenTypeHex:
-            return "Hex";
+            return "TokenTypeHex";
         case TokenTypeBinary:
-            return "Binary";
+            return "TokenTypeBinary";
         case TokenTypeFloat:
-            return "Float";
+            return "TokenTypeFloat";
         case TokenTypeChar:
-            return "Char";
+            return "TokenTypeChar";
         case TokenTypeString:
-            return "String";
+            return "TokenTypeString";
         case TokenTypeIf:
-            return "If";
+            return "TokenTypeIf";
         case TokenTypeElse:
-            return "Else";
+            return "TokenTypeElse";
+        case TokenTypeLoop:
+            return "TokenTypeLoop";
         case TokenTypeWhile:
-            return "While";
+            return "TokenTypeWhile";
+        case TokenTypeFor:
+            return "TokenTypeFor";
+        case TokenTypeIn:
+            return "TokenTypeIn";
         case TokenTypeBreak:
-            return "Break";
+            return "TokenTypeBreak";
+        case TokenTypeLet:
+            return "TokenTypeLet";
+        case TokenTypeMatch:
+            return "TokenTypeMatch";
+        case TokenTypeFalse:
+            return "TokenTypeFalse";
+        case TokenTypeTrue:
+            return "TokenTypeTrue";
+        case TokenTypeNot:
+            return "TokenTypeNot";
+        case TokenTypeAnd:
+            return "TokenTypeAnd";
+        case TokenTypeOr:
+            return "TokenTypeOr";
+        case TokenTypeFn:
+            return "TokenTypeFn";
+        case TokenTypeReturn:
+            return "TokenTypeReturn";
+        case TokenTypeMut:
+            return "TokenTypeMut";
+        case TokenTypeDefer:
+            return "TokenTypeDefer";
         case TokenTypeLParen:
-            return "LParen";
+            return "TokenTypeLParen";
         case TokenTypeRParen:
-            return "RParen";
+            return "TokenTypeRParen";
         case TokenTypeLBrace:
-            return "LBrace";
+            return "TokenTypeLBrace";
         case TokenTypeRBrace:
-            return "RBrace";
+            return "TokenTypeRBrace";
         case TokenTypeLBracket:
-            return "LBracket";
+            return "TokenTypeLBracket";
         case TokenTypeRBracket:
-            return "RBracket";
-        case TokenTypeDot:
-            return "Dot";
+            return "TokenTypeRBracket";
         case TokenTypeComma:
-            return "Comma";
+            return "TokenTypeComma";
         case TokenTypeColon:
-            return "Colon";
+            return "TokenTypeColon";
+        case TokenTypeDoubleColon:
+            return "TokenTypeDoubleColon";
+        case TokenTypeDoubleColonLt:
+            return "TokenTypeDoubleColonLt";
         case TokenTypeSemicolon:
-            return "Semicolon";
+            return "TokenTypeSemicolon";
+        case TokenTypeAmpersand:
+            return "TokenTypeAmpersand";
+        case TokenTypeUnderscore:
+            return "TokenTypeUnderscore";
+        case TokenTypeDot:
+            return "TokenTypeDot";
+        case TokenTypeDoubleDot:
+            return "TokenTypeDoubleDot";
+        case TokenTypeDoubleDotEqual:
+            return "TokenTypeDoubleDotEqual";
+        case TokenTypeDoubleDotLt:
+            return "TokenTypeDoubleDotLt";
         case TokenTypePlusEqual:
-            return "PlusEqual";
+            return "TokenTypePlusEqual";
         case TokenTypeMinusEqual:
-            return "MinusEqual";
+            return "TokenTypeMinusEqual";
         case TokenTypeAsteriskEqual:
-            return "AsteriskEqual";
+            return "TokenTypeAsteriskEqual";
         case TokenTypeSlashEqual:
-            return "SlashEqual";
+            return "TokenTypeSlashEqual";
         case TokenTypePercentEqual:
-            return "PercentEqual";
+            return "TokenTypePercentEqual";
         case TokenTypeDoubleEqual:
-            return "DoubleEqual";
+            return "TokenTypeDoubleEqual";
         case TokenTypeExclamationEqual:
-            return "ExclamationEqual";
+            return "TokenTypeExclamationEqual";
         case TokenTypeLtEqual:
-            return "LtEqual";
+            return "TokenTypeLtEqual";
         case TokenTypeGtEqual:
-            return "GtEqual";
+            return "TokenTypeGtEqual";
         case TokenTypePlus:
-            return "Plus";
+            return "TokenTypePlus";
         case TokenTypeMinus:
-            return "Minus";
+            return "TokenTypeMinus";
         case TokenTypeAsterisk:
-            return "Asterisk";
+            return "TokenTypeAsterisk";
         case TokenTypeSlash:
-            return "Slash";
+            return "TokenTypeSlash";
         case TokenTypePercent:
-            return "Percent";
+            return "TokenTypePercent";
         case TokenTypeEqual:
-            return "Equal";
+            return "TokenTypeEqual";
         case TokenTypeExclamation:
-            return "Exclamation";
+            return "TokenTypeExclamation";
         case TokenTypeLt:
-            return "Lt";
+            return "TokenTypeLt";
         case TokenTypeGt:
-            return "Gt";
+            return "TokenTypeGt";
         default:
             ASSERT_EXHAUSTIVE_MATCH();
     }
diff --git a/lexer.h b/lexer.h
index 41c1c3b..90bc787 100644
--- a/lexer.h
+++ b/lexer.h
@@ -13,6 +13,7 @@ typedef enum {
 
     TokenTypeId,
     TokenTypeInt,
+    TokenTypeIntDoubleDot,
     TokenTypeHex,
     TokenTypeBinary,
     TokenTypeFloat,
@@ -35,6 +36,8 @@ typedef enum {
     TokenTypeOr,
     TokenTypeFn,
     TokenTypeReturn,
+    TokenTypeMut,
+    TokenTypeDefer,
 
     TokenTypeLParen,
     TokenTypeRParen,
@@ -42,13 +45,17 @@ typedef enum {
     TokenTypeRBrace,
     TokenTypeLBracket,
     TokenTypeRBracket,
-    TokenTypeDot,
     TokenTypeComma,
     TokenTypeColon,
+    TokenTypeDoubleColon,
+    TokenTypeDoubleColonLt,
     TokenTypeSemicolon,
-    TokenTypeDoubleMatch,
     TokenTypeAmpersand,
     TokenTypeUnderscore,
+    TokenTypeDot,
+    TokenTypeDoubleDot,
+    TokenTypeDoubleDotEqual,
+    TokenTypeDoubleDotLt,
 
     TokenTypePlusEqual,
     TokenTypeMinusEqual,
diff --git a/main.c b/main.c
index 39f9629..17d32ad 100644
--- a/main.c
+++ b/main.c
@@ -6,8 +6,13 @@
 int main(void)
 {
     char text[]
-        = "abc 123 0xFF 0b101 3.14 'a' '\\n' \"hello\" \"world\\\"\\n\" if else /* /* while */ */ "
-          "while break (){}[].,:; += -= *= /= %= == != <= >= + - * / % % = ! < >";
+        = "abc 123 123.. 0xFF 0b101 .5 1. 3.14 'a' '\\n' \"hello\" "
+          "\"world\\\"\\n\" if else /* /* while */ */ "
+          "while for in // in \n break let match false true not and or fn "
+          "return mut "
+          "defer (){}[],: :: ::< ; & _ . .. ..= ..< += -= *= /= %= == != <= >= "
+          "+ - * / % "
+          "% = ! < >";
 
     printf("text = \"%s\"\n", text);
 
diff --git a/parser.h b/parser.h
index 4775dd4..d4c5f12 100644
--- a/parser.h
+++ b/parser.h
@@ -2,10 +2,13 @@
 #define PARSER_H
 
 #include "lexer.h"
+#include <stdbool.h>
+#include <stddef.h>
 #include <stdint.h>
 
 typedef enum {
     ParsedNodeTypeError,
+
     ParsedNodeTypeInt,
     ParsedNodeTypeFloat,
     ParsedNodeTypeChar,
@@ -27,9 +30,41 @@ typedef enum {
     ParsedNodeTypeAssign,
 } ParsedNodeType;
 
-typedef struct ParsedNode {
-    ParsedNodeType node_type;
-} ParsedNode;
+typedef struct KeyValuePair KeyValuePair;
+typedef struct ParsedNode ParsedNode;
+
+struct ParsedNode {
+    ParsedNodeType type;
+    union {
+        int64_t int_value;
+        double float_value;
+        char char_value;
+        struct {
+            char* value;
+            size_t length;
+        } string;
+        bool bool_value;
+        struct {
+            ParsedNode* values;
+            size_t length;
+        } array;
+        struct {
+            KeyValuePair* pairs;
+            size_t length;
+        } dict;
+        struct {
+            ParsedNode* condition;
+            ParsedNode* truthy;
+            ParsedNode* falsy;
+        } if_node;
+    };
+};
+
+struct KeyValuePair {
+    char* key;
+    size_t key_length;
+    ParsedNode* value;
+};
 
 typedef struct {
     Lexer* lexer;