diff --git a/.gitignore b/.gitignore
index c7579fb..cbe9096 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,8 +1,10 @@
-dummykey.crt
-dummykey.key
-dummykey.pem
-index.js
-index.js.map
+/.rollup.cache/
+/_site
+/dummykey.crt
+/dummykey.key
+/dummykey.pem
+/index.js
+/index.js.map
 /lib
 /node_modules
-/_site
+/tsconfig.tsbuildinfo
diff --git a/package.json b/package.json
index f68194b..6476bf6 100644
--- a/package.json
+++ b/package.json
@@ -3,11 +3,9 @@
   "version": "0.0.0",
   "description": "vr experiments 3",
   "scripts": {
-    "compile": "tsc",
-    "compile:watch": "tsc -w",
     "rollup": "rollup -c",
     "rollup:watch": "rollup -c -w",
-    "prepare": "yarn run compile && yarn run rollup"
+    "prepare": "yarn run rollup"
   },
   "author": "Tony Garnock-Jones <tonyg@leastfixedpoint.com>",
   "dependencies": {
@@ -15,7 +13,9 @@
   },
   "devDependencies": {
     "@rollup/plugin-node-resolve": "15.0",
+    "@rollup/plugin-typescript": "10.0",
     "rollup": "3.8",
+    "tslib": "2.4",
     "typescript": "4.9"
   }
 }
diff --git a/rollup.config.mjs b/rollup.config.mjs
index 4cedf2b..b2460f9 100644
--- a/rollup.config.mjs
+++ b/rollup.config.mjs
@@ -1,11 +1,16 @@
+// -*- javascript -*-
 import resolve from '@rollup/plugin-node-resolve';
+import typescript from '@rollup/plugin-typescript';
 import path from 'path';
 
 const babylon = '@babylonjs/core/Legacy/legacy';
 
 export default {
-  input: 'lib/index.js',
-  plugins: [resolve({ browser: true })],
+  input: 'src/index.ts',
+  plugins: [
+    resolve({ browser: true }),
+    typescript({ incremental: true }),
+  ],
   external: [
     babylon,
   ],
diff --git a/yarn.lock b/yarn.lock
index f870d80..53279c7 100644
--- a/yarn.lock
+++ b/yarn.lock
@@ -19,6 +19,14 @@
     is-module "^1.0.0"
     resolve "^1.22.1"
 
+"@rollup/plugin-typescript@10.0":
+  version "10.0.1"
+  resolved "https://registry.yarnpkg.com/@rollup/plugin-typescript/-/plugin-typescript-10.0.1.tgz#270b515b116ea28320e6bb62451c4767d49072d6"
+  integrity sha512-wBykxRLlX7EzL8BmUqMqk5zpx2onnmRMSw/l9M1sVfkJvdwfxogZQVNUM9gVMJbjRLDR5H6U0OMOrlDGmIV45A==
+  dependencies:
+    "@rollup/pluginutils" "^5.0.1"
+    resolve "^1.22.1"
+
 "@rollup/pluginutils@^5.0.1":
   version "5.0.2"
   resolved "https://registry.yarnpkg.com/@rollup/pluginutils/-/pluginutils-5.0.2.tgz#012b8f53c71e4f6f9cb317e311df1404f56e7a33"
@@ -120,6 +128,11 @@ supports-preserve-symlinks-flag@^1.0.0:
   resolved "https://registry.yarnpkg.com/supports-preserve-symlinks-flag/-/supports-preserve-symlinks-flag-1.0.0.tgz#6eda4bd344a3c94aea376d4cc31bc77311039e09"
   integrity sha512-ot0WnXS9fgdkgIcePe6RHNk1WA8+muPa6cSjeR3V8K27q9BB1rTE3R1p7Hv0z1ZyAc8s6Vvv8DIyWf681MAt0w==
 
+tslib@2.4:
+  version "2.4.1"
+  resolved "https://registry.yarnpkg.com/tslib/-/tslib-2.4.1.tgz#0d0bfbaac2880b91e22df0768e55be9753a5b17e"
+  integrity sha512-tGyy4dAjRIEwI7BzsB0lynWgOpfqjUdq91XXAlIWD2OwKBH7oCl/GZG/HT4BOHrTlPMOASlMQ7veyTqpmRcrNA==
+
 typescript@4.9:
   version "4.9.4"
   resolved "https://registry.yarnpkg.com/typescript/-/typescript-4.9.4.tgz#a2a3d2756c079abda241d75f149df9d561091e78"