Say "Out of time", and stop the sheets shadowing the clock

Two things Hans spotted playing on the phone.

A blackish gradient sat across the bottom of the screen. Both sheets are
fixed to bottom:0 and pushed off with translateY(101%), but their
box-shadow is thrown 18px *upward* with a 50px blur — so a closed sheet,
sitting 1% below the viewport, blurred darkness back onto the clock and
left it there, twice over, once per sheet. The shadow now only exists on
.sheet.on. Down one column the bottom used to fade 154 to 111 over the
last 70px; it is flat 154 to the edge. An open sheet still casts exactly
what it did.

A flagged clock now reads "Out of time" over two lines in white instead
of showing 0:00, on the red the panel already turned. Sizing it off the
viewport would not work: the score lines above eat into what is left, so
a 5-point match has less room than a 1-point one on the same phone. The
stack is a size container and the words take the smaller of 23vw and
42cqh — two lines at line-height 1.04 need 2.08x the font size, so 42% of
the container leaves a tenth spare. Measured in real viewports it lands
between 52px on a 320x568 at five points and 95px on a 412x915, fitting
every combination; with two lines it is the width that binds first, "Out
of" being the long line. The other half keeps showing its own time.

Checked that normal play still shows clocks and hides the words on both
panels, and that Reset puts the flagged panel back to its clock.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

public_html/sw.js

@@ -1,5 +1,5 @@
 /* Cache-first: once installed the clock never touches the network again. */
-const CACHE = "bgclock-v15";
+const CACHE = "bgclock-v16";
 const FILES = [
   "./",
   "./index.html",