The /play-classic timer ran at double speed. startTimer() always created a new
setInterval and overwrote timerInterval without clearing the old one, so any
extra call leaked a second interval that also incremented elapsedSecs. The
visibilitychange handler calls startTimer() on "visible", and a load-time
visibilitychange (while startGame's timer is already running) stacks a second
interval — after which stopTimer() only clears one, so the leak persists and
the clock counts ~2x forever.
Guard startTimer() to no-op when an interval is already running. This fixes the
two e2e timer tests that surfaced it once the suite actually ran (they were
asserting 0:03 / 0:04 but seeing 0:06 / 0:13), and the user-visible 2x timer.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
funman300