OFFSET was renamed to OFFSET_Y in ea5a30d9 ("add pause-mode"), while
the call to `draw_leds()` in bc7e3b92 ("Add led activity to ECG app")
still uses the old name. This causes an exception and the ECG app fails
to proceed past the start screen.
for !269 with patch-1
1 minute and 4 seconds
(queued for 4 seconds)