diff --git a/README.md b/README.md
index a899097..1d28e14 100644
--- a/README.md
+++ b/README.md
@@ -152,28 +152,16 @@ docker run --rm -v (pwd):/monkey -w /monkey php:8.4-cli ./monkey run examples/fi
 Clone this repository, execute `composer install`, then:
 
 ```bash
-docker run --rm -v (pwd):/monkey -w /monkey php:8.4-cli ./monkey repl
+docker run -it --rm -v (pwd):/monkey -w /monkey php:8.4-cli ./monkey repl
 ```
 
 Example:
 
 ```text
-            __,__
-   .--.  .-"     "-.  .--.
-  / .. \/  .-. .-.  \/ .. \
- | |  '|  /   Y   \  |'  | |
- | \   \  \ 0 | 0 /  /   / |
-  \ '- ,\.-"`` ``"-./, -' /
-   `'-' /_   ^ ^   _\ '-'`
-       |  \._   _./  |
-       \   \ `~` /   /
-        '._ '-=-' _.'
-           '~---~'
--------------------------------
-| Monkey Programming Language |
--------------------------------
-
- > let a = 20 + fn(x){ return x + 10; }(2);
+🐒 Monkey Programming Language v1.0.0
+Type ':h' for help, ':c' for clear, ':q' to quit
+
+➜ let a = 20 + fn(x){ return x + 10; }(2);
 32
 ```
 
diff --git a/composer.json b/composer.json
index 9f0a378..bc332ec 100644
--- a/composer.json
+++ b/composer.json
@@ -9,7 +9,8 @@
     "rector/rector": "^2.0.3"
   },
   "require": {
-    "php": "^8.4"
+    "php": "^8.4",
+    "ext-readline": "*"
   },
   "autoload": {
     "psr-4": {
diff --git a/monkey b/monkey
index cb421b4..eb78a6d 100755
--- a/monkey
+++ b/monkey
@@ -3,10 +3,17 @@
 
 declare(strict_types=1);
 
+require 'vendor/autoload.php';
+
+use Monkey\Monkey;
+
 if (PHP_SAPI !== 'cli') {
     exit;
 }
 
-require 'vendor/autoload.php';
+if (!isset($GLOBALS['argv']) || !is_array($GLOBALS['argv'])) {
+    exit(1);
+}
 
-require __DIR__ . '/src/monkey.php';
+$cli = new Monkey();
+exit($cli->run($GLOBALS['argv']));
diff --git a/src/Monkey.php b/src/Monkey.php
new file mode 100644
index 0000000..f024a2f
--- /dev/null
+++ b/src/Monkey.php
@@ -0,0 +1,246 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Monkey;
+
+use JetBrains\PhpStorm\NoReturn;
+use Monkey\Evaluator\Environment;
+use Monkey\Evaluator\Evaluator;
+use Monkey\Lexer\Lexer;
+use Monkey\Object\MonkeyObject;
+use Monkey\Object\NullObject;
+use Monkey\Parser\Parser;
+use Monkey\Parser\ProgramParser;
+use RuntimeException;
+use Throwable;
+
+use function count;
+
+use const PHP_EOL;
+use const STDERR;
+
+final class Monkey
+{
+    private const string VERSION = '1.0.0';
+
+    private readonly Environment $environment;
+
+    private bool $debugMode = false;
+
+    public function __construct()
+    {
+        $this->environment = new Environment();
+    }
+
+    /**
+     * @param array<string> $argv
+     */
+    public function run(array $argv): int
+    {
+        if (count($argv) <= 1) {
+            return $this->showHelp();
+        }
+
+        try {
+            return match ($argv[1]) {
+                'repl' => $this->startRepl(),
+                'run' => $this->runFile($argv[2] ?? null),
+                '--version', '-v' => $this->showVersion(),
+                '--help', '-h' => $this->showHelp(),
+                '--debug' => $this->enableDebugMode(),
+                default => $this->showHelp(),
+            };
+        } catch (Throwable $throwable) {
+            $this->writeError($throwable->getMessage());
+
+            return 1;
+        }
+    }
+
+    private function startRepl(): int
+    {
+        $this->showWelcomeBanner();
+
+        while (true) {
+            $input = $this->readInput();
+
+            if ($input === false) {
+                echo PHP_EOL . 'Goodbye!' . PHP_EOL;
+
+                return 0;
+            }
+
+            if (trim($input) === '') {
+                continue;
+            }
+
+            if ($this->handleSpecialCommand($input)) {
+                continue;
+            }
+
+            try {
+                $this->writeOutput($this->evaluate($input));
+            } catch (Throwable $e) {
+                $this->writeError($e->getMessage());
+            }
+        }
+    }
+
+    private function runFile(?string $filename): int
+    {
+        if ($filename === null) {
+            throw new RuntimeException('No input file specified');
+        }
+
+        if (!file_exists($filename)) {
+            throw new RuntimeException("File not found: {$filename}");
+        }
+
+        $contents = file_get_contents($filename);
+
+        if ($contents === false) {
+            throw new RuntimeException("Could not read file: {$filename}");
+        }
+
+        $this->writeOutput($this->evaluate($contents));
+
+        return 0;
+    }
+
+    private function evaluate(string $input): MonkeyObject
+    {
+        $lexer = new Lexer($input);
+        $parser = new Parser($lexer);
+
+        $errors = $parser->errors();
+
+        if ($errors !== []) {
+            throw new RuntimeException("Parser errors:\n" . implode("\n", $errors));
+        }
+
+        $program = new ProgramParser()($parser);
+        $evaluator = new Evaluator();
+
+        return $evaluator->eval($program, $this->environment);
+    }
+
+    private function handleSpecialCommand(string $input): bool
+    {
+        return match (trim($input)) {
+            ':q', ':quit', 'exit' => $this->handleQuit(),
+            ':h', ':help' => $this->handleHelp(),
+            ':c', ':clear' => $this->handleClear(),
+            ':d', ':debug' => $this->handleDebugToggle(),
+            default => false,
+        };
+    }
+
+    #[NoReturn] private function handleQuit(): bool
+    {
+        echo 'Goodbye!' . PHP_EOL;
+
+        exit(0);
+    }
+
+    private function handleHelp(): bool
+    {
+        echo <<<HELP
+        \nMonkey REPL Commands:
+        :q, :quit, exit   Exit the REPL
+        :h, :help         Show this help message
+        :c, :clear        Clear the screen
+        :d, :debug        Toggle debug mode
+
+        Press Ctrl+C to cancel current input
+        HELP . PHP_EOL;
+
+        return true;
+    }
+
+    private function handleClear(): bool
+    {
+        system('clear');
+
+        $this->showWelcomeBanner();
+
+        return true;
+    }
+
+    private function handleDebugToggle(): bool
+    {
+        $this->debugMode = !$this->debugMode;
+
+        echo 'Debug mode: ' . ($this->debugMode ? 'Enabled' : 'Disabled') . PHP_EOL;
+
+        return true;
+    }
+
+    private function showWelcomeBanner(): void
+    {
+        $version = self::VERSION;
+
+        echo <<<BANNER
+        🐒 Monkey Programming Language v{$version}
+        Type ':h' for help, ':c' for clear, ':q' to quit
+        BANNER . PHP_EOL . PHP_EOL;
+    }
+
+    private function readInput(): string | false
+    {
+        return readline("\n➜ ");
+    }
+
+    private function writeOutput(MonkeyObject $result): void
+    {
+        // Skip output for NullObject unless in debug mode
+        if ($result instanceof NullObject && !$this->debugMode) {
+            return;
+        }
+
+        if ($this->debugMode) {
+            echo $result::class . ': ';
+        }
+
+        echo $result->inspect() . PHP_EOL;
+    }
+
+    private function writeError(string $message): void
+    {
+        fwrite(STDERR, 'Error: ' . $message . PHP_EOL);
+    }
+
+    private function showVersion(): int
+    {
+        echo 'Monkey Programming Language v' . self::VERSION . PHP_EOL;
+
+        return 0;
+    }
+
+    private function showHelp(): int
+    {
+        echo <<<HELP
+        Usage: monkey [command]
+
+        Commands:
+            repl              Start the interactive REPL
+            run <file>        Execute a Monkey source file
+            --version, -v     Show version information
+            --help, -h        Show this help message
+            --debug           Enable debug mode
+
+        Examples:
+            monkey repl
+            monkey run example.monkey
+        HELP . PHP_EOL;
+
+        return 0;
+    }
+
+    private function enableDebugMode(): int
+    {
+        $this->debugMode = true;
+
+        return $this->startRepl();
+    }
+}
diff --git a/src/monkey.php b/src/monkey.php
deleted file mode 100644
index d1aca71..0000000
--- a/src/monkey.php
+++ /dev/null
@@ -1,35 +0,0 @@
-<?php
-
-declare(strict_types=1);
-
-namespace Monkey;
-
-use Monkey\Evaluator\Environment;
-use Monkey\Repl\Repl;
-
-function help(): never
-{
-    echo <<<HELP
-    Usage: monkey [command]
-
-    Commands:
-        repl
-            Start the Repl.
-        run file.mk
-            Runs a file contents.
-        help
-            This help.
-    HELP;
-
-    exit;
-}
-
-if ($argc <= 1) {
-    help();
-}
-
-match ($argv[1]) {
-    'repl' => Repl::start(),
-    'run' => Repl::eval((string)file_get_contents($argv[2]), new Environment()),
-    default => help(),
-};