smaller stage, half steps above 2x — bigger, still even

Trimming the stage alone does nothing, and that is worth writing down: the
scale is snapped, so at 3x the game is 1512 device pixels wide whether the
stage is 560 or 512. Shrinking the surround only pays when it crosses a step.
So both halves land together.

── the stage ──

560x400 down to 512x352, which is expert (504x342, measured) plus four pixels
a side. There is nothing left to give — intermediate is 342 tall too, so
anything shorter clips a board people actually play.

── half steps from 2x ──

Not a retreat from whole-number scaling. The unit that has to stay regular is
the CELL, not the pixel: this is a 16px grid, so at 3.5x a cell is exactly 56
screen pixels — as even as 3x or 4x — and only sub-cell pixels alternate
between three and four. Below 2x that alternation is a third of a pixel rather
than a seventh, so whole numbers still apply there. The case that started all
this, a fractional devicePixelRatio at nominal 1:1, put the CELL boundaries at
26.4px, which is a different thing entirely.

Together, on a 1800x1400 device-pixel panel: 3.0x becomes 3.5x, and the game
goes from 1512 to 1764 device pixels wide.

Known cost, and it is in the README: the Extras > Auto Options dialog is 328
wide and opens 25px right of the game, so it needs a 554-wide stage to fit
whole from beginner. It cannot be closed from the panel anyway — no window
manager, no title bar, no OK button — so that is the thing to fix before this
number is revisited.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Officer-Session: de3ed4e6-f88a-429c-94e6-a760336ba83b

README.md

@@ -77,7 +77,7 @@ The check that matters is `ss -lntp` against the **running** process. Reading th
 listener that exists because a flag is missing, and running the same arguments by hand did not reproduce
 it either.
 
-**The game is centred on a fixed stage, and the whole stage is what you see.** The framebuffer is 560x400
+**The game is centred on a fixed stage, and the whole stage is what you see.** The framebuffer is 512x352
 whatever the difficulty, `sidecar/session.ts` keeps the window in the middle of it, and the panel draws the
 framebuffer entire — scaled to fit, never cropped. So changing difficulty moves the board rather than
 resizing the panel, and the surround is teal (`-solid`) rather than the root's black.
@@ -85,10 +85,16 @@ resizing the panel, and the surround is teal (`-solid`) rather than the root's b
 **The stage is small because the panel scales it by whole numbers.** Pixel art at a fractional scale gets
 uneven cells — some three screen pixels wide, their neighbours two — which reads as "not quite right"
 rather than as blur, and `image-rendering: pixelated` does not help because unevenness is not blur. So the
-panel picks the largest whole number of DEVICE pixels per source pixel and every pixel of empty stage is
-panel the game does not get: in an 1866-device-pixel panel, 800 wide lands on 2x and 560 wide lands on 3x.
-560x400 is expert (504x342) plus a margin. A custom board bigger than that is clipped at the right and
-bottom rather than shrunk, with the menu bar kept reachable.
+panel snaps the scale, in DEVICE pixels, to whole numbers below 2x and half steps above it. Halves are safe
+because the unit that has to stay regular is the CELL: at 3.5x a cell is exactly 56 screen pixels, as even
+as at 3x, and only sub-cell pixels alternate.
+
+That makes the size QUANTISED, which is the thing to understand before changing the stage: at 3x the game
+is the same width whether the stage is 512 or 560. Trimming the surround is worth nothing on its own — it
+only helps when it crosses a step. 512x352 is expert (504x342) plus four pixels a side, and there is no
+room left: intermediate is 342 tall too. A custom board bigger than that is clipped at the right and bottom
+rather than shrunk, with the menu bar kept reachable, and the Auto Options dialog needs a 554-wide stage to
+fit whole from beginner.
 
 It used to park the window at the origin and have the client crop to the window's size, polled every four
 seconds. That resized the panel under the player, and it was off by the 3x29 wine puts between the root