diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 0922e66b..8fb773f7 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -57,6 +57,19 @@ jobs:
               run: npm install
             - name: Check Types
               run: npm run test:types
+    are_the_types_wrong:
+        name: Are the types wrong?
+        runs-on: ubuntu-latest
+        steps:
+            - uses: actions/checkout@v6
+            - name: Setup Node.js
+              uses: actions/setup-node@v6
+              with:
+                  node-version: "lts/*"
+            - name: Install Packages
+              run: npm install
+            - name: Check validity of type definitions
+              run: npm run lint:types
     jsr_test:
         name: Verify JSR Publish
         runs-on: ubuntu-latest
diff --git a/jsr.json b/jsr.json
index 54039f05..dd2cb3e2 100644
--- a/jsr.json
+++ b/jsr.json
@@ -2,11 +2,11 @@
   "name": "@eslint/css",
   "version": "0.14.1",
   "exports": {
-    ".": "./dist/esm/index.js"
+    ".": "./dist/index.js"
   },
   "publish": {
     "include": [
-      "dist/esm",
+      "dist",
       "README.md",
       "jsr.json",
       "LICENSE"
diff --git a/package.json b/package.json
index 14dd6c0b..73a338f5 100644
--- a/package.json
+++ b/package.json
@@ -4,26 +4,15 @@
   "description": "CSS linting plugin for ESLint",
   "author": "Nicholas C. Zakas",
   "type": "module",
-  "main": "dist/esm/index.js",
-  "types": "dist/esm/index.d.ts",
+  "main": "dist/index.js",
+  "types": "dist/index.d.ts",
   "exports": {
     ".": {
-      "require": {
-        "types": "./dist/cjs/index.d.cts",
-        "default": "./dist/cjs/index.cjs"
-      },
-      "import": {
-        "types": "./dist/esm/index.d.ts",
-        "default": "./dist/esm/index.js"
-      }
+      "types": "./dist/index.d.ts",
+      "default": "./dist/index.js"
     },
     "./types": {
-      "require": {
-        "types": "./dist/cjs/types.cts"
-      },
-      "import": {
-        "types": "./dist/esm/types.d.ts"
-      }
+      "types": "./dist/types.d.ts"
     }
   },
   "files": [
@@ -40,11 +29,8 @@
       "eslint --fix",
       "prettier --write"
     ],
-    "README.md": [
-      "npm run build:update-rules-docs"
-    ],
     "!(*.js)": "prettier --write --ignore-unknown",
-    "{src/rules/*.js,tools/update-rules-docs.js}": [
+    "{src/rules/*.js,tools/update-rules-docs.js,README.md}": [
       "npm run build:update-rules-docs",
       "git add README.md"
     ]
@@ -58,21 +44,21 @@
   },
   "homepage": "https://github.com/eslint/css#readme",
   "scripts": {
-    "build:dedupe-types": "node tools/dedupe-types.js dist/cjs/index.cjs dist/esm/index.js",
-    "build:cts": "node -e \"fs.copyFileSync('dist/esm/index.d.ts', 'dist/cjs/index.d.cts')\" && node tools/update-cts.js dist/cjs/types.cts dist/cjs/index.d.cts",
+    "build": "npm run build:rules && npm run build:types && npm run build:update-rules-docs",
+    "build:baseline": "node tools/generate-baseline.js",
     "build:rules": "node tools/build-rules.js",
-    "build": "npm run build:rules && rollup -c && npm run build:dedupe-types && tsc -p tsconfig.esm.json && npm run build:cts",
+    "build:types": "tsc",
     "build:update-rules-docs": "node tools/update-rules-docs.js",
-    "build:baseline": "node tools/generate-baseline.js",
     "prepare": "npm run build",
     "pretest": "npm run build",
     "lint": "eslint",
     "lint:fix": "eslint --fix",
+    "lint:types": "attw --pack --profile esm-only",
     "fmt": "prettier --write .",
     "fmt:check": "prettier --check .",
     "test": "mocha \"tests/**/*.test.js\"",
     "test:coverage": "c8 npm test",
-    "test:jsr": "npx jsr@latest publish --dry-run",
+    "test:jsr": "npx -y jsr@latest publish --dry-run",
     "test:types": "npm run build && tsc -p tests/types/tsconfig.json"
   },
   "keywords": [
@@ -89,6 +75,7 @@
     "@eslint/plugin-kit": "^0.5.0"
   },
   "devDependencies": {
+    "@arethetypeswrong/cli": "^0.18.2",
     "@eslint/json": "^0.14.0",
     "c8": "^10.1.3",
     "dedent": "^1.5.3",
@@ -101,9 +88,6 @@
     "mdn-data": "^2.25.0",
     "mocha": "^11.0.0",
     "prettier": "^3.7.3",
-    "rollup": "^4.52.3",
-    "rollup-plugin-copy": "^3.5.0",
-    "rollup-plugin-delete": "^3.0.1",
     "tailwind-csstree": "^0.1.0",
     "typescript": "^5.9.2",
     "web-features": "^3.12.0",
diff --git a/rollup.config.js b/rollup.config.js
deleted file mode 100644
index 84b6c269..00000000
--- a/rollup.config.js
+++ /dev/null
@@ -1,32 +0,0 @@
-import copy from "rollup-plugin-copy";
-import del from "rollup-plugin-delete";
-
-export default [
-	{
-		input: "src/index.js",
-		output: [
-			{
-				file: "dist/cjs/index.cjs",
-				format: "cjs",
-			},
-			{
-				file: "dist/esm/index.js",
-				format: "esm",
-				banner: '// @ts-self-types="./index.d.ts"',
-			},
-		],
-		plugins: [
-			del({ targets: ["dist/*"] }),
-			copy({
-				targets: [
-					{
-						src: "src/types.ts",
-						dest: "dist/cjs",
-						rename: "types.cts",
-					},
-					{ src: "src/types.ts", dest: "dist/esm" },
-				],
-			}),
-		],
-	},
-];
diff --git a/tools/dedupe-types.js b/tools/dedupe-types.js
deleted file mode 100644
index 054ba126..00000000
--- a/tools/dedupe-types.js
+++ /dev/null
@@ -1,87 +0,0 @@
-/**
- * @fileoverview Strips typedef aliases from the rolled-up file. This
- * is necessary because the TypeScript compiler throws an error when
- * it encounters a duplicate typedef.
- *
- * Usage:
- *  node tools/dedupe-types.js filename1.js filename2.js ...
- *
- * @author Nicholas C. Zakas
- */
-
-//-----------------------------------------------------------------------------
-// Imports
-//-----------------------------------------------------------------------------
-
-import fs from "node:fs";
-
-//-----------------------------------------------------------------------------
-// Main
-//-----------------------------------------------------------------------------
-
-const importRegExp =
-	/^\s*\*\s*@import\s*\{(?<ids>[^,}]+(?:,[^,}]+)*)\}\s*from\s*"(?<source>[^"]+)"/u;
-
-// read files from the command line
-const files = process.argv.slice(2);
-
-files.forEach(filePath => {
-	const lines = fs.readFileSync(filePath, "utf8").split(/\r?\n/gu);
-	const imports = new Map();
-
-	// find all imports and remove them
-	const remainingLines = lines.filter(line => {
-		if (!line.startsWith(" * @import")) {
-			return true;
-		}
-
-		const match = importRegExp.exec(line);
-
-		if (!match) {
-			throw Error("@import statement must be on a single line.");
-		}
-
-		const source = match.groups.source;
-		const ids = match.groups.ids.split(/,/gu).map(id => id.trim());
-
-		// save the import data
-
-		if (!imports.has(source)) {
-			imports.set(source, new Set());
-		}
-
-		const existingIds = imports.get(source);
-		ids.forEach(id => existingIds.add(id));
-
-		return false;
-	});
-
-	// create a new import statement for each unique import
-	const jsdocBlock = ["/**"];
-
-	imports.forEach((ids, source) => {
-		// if it's a local file, we don't need it
-		if (source.startsWith("./")) {
-			return;
-		}
-
-		const idList = Array.from(ids).join(", ");
-		jsdocBlock.push(` * @import { ${idList} } from "${source}"`);
-	});
-
-	// add the new import statements to the top of the file
-	jsdocBlock.push(" */");
-	remainingLines.unshift(...jsdocBlock);
-	remainingLines.unshift(""); // add a blank line before the block
-
-	// replace references to ../types.ts with ./types.ts
-	let text = remainingLines
-		.join("\n")
-		.replace(/\.\.\/types\.js/gu, "./types.js");
-
-	if (filePath.endsWith(".cjs")) {
-		text = text.replace("types.js", "types.cjs");
-	}
-
-	fs.writeFileSync(filePath, text, "utf8");
-});
diff --git a/tools/update-cts.js b/tools/update-cts.js
deleted file mode 100644
index b394d091..00000000
--- a/tools/update-cts.js
+++ /dev/null
@@ -1,29 +0,0 @@
-/**
- * @fileoverview Replaces all .js references with .cjs references.
- *
- * Usage:
- *  node tools/update-cts.js filename1.js filename2.js ...
- *
- * @author Nicholas C. Zakas
- */
-
-//-----------------------------------------------------------------------------
-// Imports
-//-----------------------------------------------------------------------------
-
-import fs from "node:fs";
-
-//-----------------------------------------------------------------------------
-// Main
-//-----------------------------------------------------------------------------
-
-// read files from the command line
-const files = process.argv.slice(2);
-
-files.forEach(filePath => {
-	let text = fs.readFileSync(filePath, "utf8");
-
-	text = text.replace(/(\.\/(index|types))\.js/gu, "$1.cjs");
-
-	fs.writeFileSync(filePath, text, "utf8");
-});
diff --git a/tsconfig.esm.json b/tsconfig.esm.json
deleted file mode 100644
index 40ece132..00000000
--- a/tsconfig.esm.json
+++ /dev/null
@@ -1,4 +0,0 @@
-{
-  "extends": "./tsconfig.json",
-  "files": ["dist/esm/index.js"]
-}
diff --git a/tsconfig.json b/tsconfig.json
index 27f027ba..25070aa8 100644
--- a/tsconfig.json
+++ b/tsconfig.json
@@ -1,11 +1,10 @@
 {
-  "files": ["src/index.js"],
+  "include": ["src/**/*.js", "src/**/*.ts"],
   "compilerOptions": {
     "declaration": true,
-    "emitDeclarationOnly": true,
     "allowJs": true,
     "checkJs": true,
-    "outDir": "dist/esm",
+    "outDir": "dist",
     "skipLibCheck": true,
     "target": "ES2022",
     "lib": ["ES2022"],