:root {
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 28px;
  --space-7: 40px;
  --space-8: 56px;
  --space-9: 80px;
  --tile-gap: 2px;        /* between tiles in a row */
  --row-gap: 12px;        /* between rows on the board */
  --board-pad: 16px 20px 18px;
  --page-pad: 20px;       /* phone */
  --page-pad-desktop: 40px;
  --measure: 60ch;        /* reading width */
  --board-cols-phone: 20; /* tiles per row on a phone */
  --board-cols: 34;       /* tiles per row at 680px */
}