diff --git a/package.json b/package.json
index 1ca35eb..5854c4b 100644
--- a/package.json
+++ b/package.json
@@ -6,6 +6,7 @@
   "license": "MIT",
   "main": "hex-color-picker.js",
   "module": "hex-color-picker.js",
+  "type": "module",
   "types": "hex-color-picker.d.ts",
   "repository": {
     "type": "git",
@@ -66,14 +67,14 @@
     "build": "npm run styles && tsc",
     "deploy": "npm run dist && gh-pages -d dist",
     "dev": "npm run watch & npm run serve",
-    "dist": "npm run build && rimraf dist && rollup -c rollup.config.js",
+    "dist": "npm run build && rimraf dist && rollup -c rollup.config.cjs",
     "lint": "eslint src --ext .ts",
     "prepublishOnly": "npm run build && npm run analyze",
     "release": "standard-version",
     "serve": "web-dev-server --node-resolve --open",
     "size": "npm run build && size-limit",
     "start": "web-dev-server --app-index dist/index.html --open",
-    "styles": "node ./scripts/build-styles.js",
+    "styles": "node ./scripts/build-styles.cjs",
     "test": "wtr src/test/*.ts --coverage",
     "test:visual": "wtr src/test/visual/*.ts",
     "test:update": "UPDATE_REFS=true wtr src/test/visual/*.ts",
diff --git a/rollup.config.js b/rollup.config.cjs
similarity index 100%
rename from rollup.config.js
rename to rollup.config.cjs
diff --git a/scripts/build-styles.js b/scripts/build-styles.cjs
similarity index 94%
rename from scripts/build-styles.js
rename to scripts/build-styles.cjs
index d33c08c..b41c563 100644
--- a/scripts/build-styles.js
+++ b/scripts/build-styles.cjs
@@ -10,7 +10,7 @@ const readFile = util.promisify(fs.readFile);
 const delimiter = /<%\s*content\s*%>/;
 
 async function minifyCss(cssFile) {
-  const data = await readFile(cssFile);
+  const data = await readFile(cssFile, 'utf8');
   const result = csso.minify(data);
   return result.css;
 }
diff --git a/web-test-runner.config.js b/web-test-runner.config.js
index 0dd6975..0ec7ba3 100644
--- a/web-test-runner.config.js
+++ b/web-test-runner.config.js
@@ -1,7 +1,7 @@
-const { esbuildPlugin } = require('@web/dev-server-esbuild');
-const { visualRegressionPlugin } = require('@web/test-runner-visual-regression/plugin');
+import { esbuildPlugin } from '@web/dev-server-esbuild';
+import { visualRegressionPlugin } from '@web/test-runner-visual-regression/plugin';
 
-module.exports = {
+export default {
   nodeResolve: true,
   plugins: [
     esbuildPlugin({ ts: true }),