Add border-box box-sizing

form/style.css

@@ -14,6 +14,14 @@
 /* Add nodebug class to any parent field (e.g. body) to turn off coloring */
 .nodebug { --color-form: transparent; --color-field: transparent; --color-label: transparent; --color-input: transparent; }
 
+html {
+  box-sizing: border-box;
+}
+
+*, *::before, *::after {
+  box-sizing: inherit;
+}
+
 body {
   display: flex;
   flex-direction: column;
@@ -23,4 +31,3 @@ body {
 .body--centered {
   align-items: center;
 }
-