restore grid keyboard focus on load and cell click

frontend/src/components/Grid.tsx

@@ -14,6 +14,15 @@ function getCellSize(gridSize: number): number {
   return 36
 }
 
+function firstWhiteIdx(cells: string[][], width: number): number {
+  for (let r = 0; r < cells.length; r++) {
+    for (let c = 0; c < cells[r].length; c++) {
+      if (cells[r][c] !== 'black') return r * width + c
+    }
+  }
+  return 0
+}
+
 export default function Grid() {
   const { t } = useTranslation()
   const svgRef = useRef<SVGSVGElement>(null)
@@ -42,6 +51,22 @@ export default function Grid() {
     cellRefs.current[idx]?.focus()
   }, [selectedCell, width])
 
+  // land focus on the starting cell when a puzzle loads and nothing else has
+  // it, so typing works without clicking into the grid first
+  useEffect(() => {
+    if (!puzzle) return
+    const t = setTimeout(() => {
+      const active = document.activeElement
+      if (active !== document.body && active !== null) return
+      const st = useStore.getState()
+      const idx = st.selectedCell
+        ? st.selectedCell.row * width + st.selectedCell.col
+        : firstWhiteIdx(puzzle.cells, width)
+      cellRefs.current[idx]?.focus({ preventScroll: true })
+    }, 0)
+    return () => clearTimeout(t)
+  }, [puzzle, width])
+
   if (!puzzle) return null
 
   const CELL = getCellSize(Math.max(width, height))
@@ -110,25 +135,23 @@ export default function Grid() {
   }
 
   const focusTypingField = (r: number, c: number) => {
-    if (!window.matchMedia('(pointer: coarse)').matches) return
+    if (window.matchMedia('(pointer: coarse)').matches) {
       const field = typingRef.current
       if (field) {
         field.setAttribute('aria-label', buildCellLabel(r, c))
         field.focus({ preventScroll: true })
       }
+    } else {
+      // desktop: park focus on the matching grid cell so keystrokes reach it
+      cellRefs.current[r * width + c]?.focus()
+    }
   }
 
   // Exactly one cell is a Tab stop so the grid can receive keyboard focus even
   // before a cell has been selected.
-  const focusableIdx = (() => {
-    if (selectedCell) return selectedCell.row * width + selectedCell.col
-    for (let r = 0; r < height; r++) {
-      for (let c = 0; c < width; c++) {
-        if (puzzle.cells[r][c] !== 'black') return r * width + c
-      }
-    }
-    return 0
-  })()
+  const focusableIdx = selectedCell
+    ? selectedCell.row * width + selectedCell.col
+    : firstWhiteIdx(puzzle.cells, width)
 
   return (
     <div
@@ -178,7 +201,13 @@ export default function Grid() {
                 id={`cell-${r}-${c}`}
                 data-cell={`${r},${c}`}
                 onClick={() => {
-                  if (isBlack) return
+                  if (isBlack) {
+                    // keep keyboard focus inside the grid after tapping a black square
+                    if (!window.matchMedia('(pointer: coarse)').matches) {
+                      cellRefs.current[focusableIdx]?.focus()
+                    }
+                    return
+                  }
                   selectCell(r, c)
                   focusTypingField(r, c)
                 }}