diff --git a/tdkpin-rs/web/README.md b/tdkpin-rs/web/README.md
index bd5f68a..083786e 100644
--- a/tdkpin-rs/web/README.md
+++ b/tdkpin-rs/web/README.md
@@ -6,9 +6,10 @@ Build and serve the browser version from this directory with:
 just web-serve
 ```
 
-The game is compiled for `wasm32-unknown-unknown` and loaded into the centered
-black canvas by `index.html`. Browser settings and high scores are saved in
-`localStorage`; native builds continue to use their normal per-user save file.
+The game is compiled for `wasm32-unknown-unknown` and loaded into a fixed
+640x460 canvas centered on the black page by `index.html`. Browser settings and
+high scores are saved in `localStorage`; native builds continue to use their
+normal per-user save file.
 
 The page uses Macroquad's official browser loader from the miniquad samples
 site. The web page must be served over HTTP rather than opened directly from a
diff --git a/tdkpin-rs/web/index.html b/tdkpin-rs/web/index.html
index 66153c5..56965b4 100644
--- a/tdkpin-rs/web/index.html
+++ b/tdkpin-rs/web/index.html
@@ -22,7 +22,9 @@
         width: 100%;
         height: 100%;
         margin: 0;
-        overflow: hidden;
+        min-width: 640px;
+        min-height: 460px;
+        overflow: auto;
         background: #000;
       }
 
@@ -33,8 +35,8 @@
 
       #glcanvas {
         display: block;
-        width: 100vw;
-        height: 100vh;
+        width: 640px;
+        height: 460px;
         background: #000;
         outline: none;
         image-rendering: pixelated;