diff --git a/docker/frontend/src/Library.tsx b/docker/frontend/src/Library.tsx
index d88d0cd..fff2e1a 100644
--- a/docker/frontend/src/Library.tsx
+++ b/docker/frontend/src/Library.tsx
@@ -3070,6 +3070,12 @@ function useWallWindow(count: number, on: boolean): { ref: RefObject<HTMLDivElem
   // stands at.
   const winRef = useRef(win);
   const measureRef = useRef<() => void>(() => {});
+  // The step from one row to the next, taken once per column count and kept. It
+  // is a ref rather than a value read on every pass because the pass reads it off
+  // the rows the window drew — and a step that moves with the window is a window
+  // that moves with the step: the two trade places forever (see `measure`).
+  const pitchRef = useRef(0);
+  const colsRef = useRef(0);
   // The window over a scroll container is taken rather than kept, so it is taken
   // after every render: the first pass draws a screenful, the next reads the row's
   // step off it and lays out the spacers, and the pass after that leaves both
@@ -3108,7 +3114,23 @@ function useWallWindow(count: number, on: boolean): { ref: RefObject<HTMLDivElem
       // not in hand.
       const rowsDrawn = Math.floor(cards.length / cols);
       if (rowsDrawn < 2) return;
-      const pitch = (cards[(rowsDrawn - 1) * cols].getBoundingClientRect().top - cards[0].getBoundingClientRect().top) / (rowsDrawn - 1);
+      // The step is read off the drawn rows the first time the wall stands at this
+      // many columns, and kept until it stands at another: the average of a run of
+      // rows moves as the run grows, so a step re-read on every pass made the window
+      // depend on itself — `to` traded places with a second sum a row away, sixty
+      // times a second, until React gave up with #185 and the screen went blank. One
+      // step, one window. It is re-read when the wall re-columns, the only thing that
+      // changes a card's own height (a caption wraps at the width it is given); a
+      // resize that does not re-column keeps the step, and a spacer a few pixels out
+      // is a scrollbar a few pixels out, not a blank screen.
+      if (colsRef.current !== cols) {
+        const drawn = (cards[(rowsDrawn - 1) * cols].getBoundingClientRect().top - cards[0].getBoundingClientRect().top) / (rowsDrawn - 1);
+        if (drawn > 0) {
+          colsRef.current = cols;
+          pitchRef.current = drawn;
+        }
+      }
+      const pitch = pitchRef.current;
       if (!(pitch > 0)) return;
       const rows = Math.ceil(count / cols);
       const row0 = Math.max(0, Math.floor(el.scrollTop / pitch) - WALL_ROWS);