Phase 2, step 1 — find out what this device can actually do.
(no JavaScript at all)
Tap Run the test, then get as many fingers as you can on the + and − buttons at once — ideally six, held down — for the full 15 seconds. This is the exact hot-path design the real app will use, so its numbers are the ones that matter.
Rendered by React with real Tailwind v4 classes. check.js reads the computed styles off it — if this box is unstyled or invisible, Tailwind v4 does not work on this device.
Only needed if the send above failed.