diff --git a/bin/index.js b/bin/index.js
new file mode 100644
index 0000000..6c9c079
--- /dev/null
+++ b/bin/index.js
@@ -0,0 +1,36 @@
+// @ts-check
+const fs = require('fs');
+const zlib = require('zlib');
+const { minify } = require('terser');
+const pkg = require('../package.json');
+
+/**
+ * @param {string} file
+ * @param {string} source
+ */
+function write(file, source) {
+	let isModule = !source.startsWith('!function');
+	let result = minify(source, {
+		module: isModule,
+		compress: true,
+	});
+
+	fs.writeFileSync(file, result.code);
+	console.log('~> "%s" (%d b)', file, zlib.gzipSync(result.code).byteLength);
+}
+
+let input = fs.readFileSync('src/index.js', 'utf8');
+
+// copy for ESM
+write(pkg.module, input);
+
+// transform ESM -> CJS exports
+write(pkg.main, input.replace('export function', 'function').replace(
+	'export default clsx;',
+	'module.exports = clsx;\n'
+	+ 'module.exports.clsx = clsx;'
+));
+
+// transform ESM -> UMD exports
+input = input.replace('export function', 'function').replace('export default clsx;', 'return clsx.clsx=clsx, clsx;');
+write(pkg.unpkg, '!function(global,factory){"object"==typeof exports&&"undefined"!=typeof module?module.exports=factory():"function"==typeof define&&define.amd?define(factory):global.clsx=factory()}(this,function(){' + input + '});');
diff --git a/package.json b/package.json
index 6721305..e75cfad 100644
--- a/package.json
+++ b/package.json
@@ -17,7 +17,7 @@
     "node": ">=6"
   },
   "scripts": {
-    "build": "bundt",
+    "build": "node bin",
     "test": "uvu -r esm test"
   },
   "files": [
@@ -30,8 +30,8 @@
     "classnames"
   ],
   "devDependencies": {
-    "bundt": "1.0.1",
     "esm": "3.2.25",
-    "uvu": "0.5.4"
+    "terser": "4.8.0",
+    "uvu": "0.5.6"
   }
 }