/* Raster grid subsystem (rsms.me/raster) */
r-grid {
  display: grid;
  --grid-tc: repeat(4, 1fr);
  grid-template-columns: var(--grid-tc);
  --grid-cs: 1; /* column start */
  --grid-ce: -1 /* column end */
}

/* r-cell -- cell or column */
r-grid > r-cell { display: block; appearance: none; -webkit-appearance: none }

r-grid[columns="1"] { --grid-tc: repeat(1, 1fr) }
r-grid[columns="2"] { --grid-tc: repeat(2, 1fr) }
r-grid[columns="3"] { --grid-tc: repeat(3, 1fr) }
r-grid[columns="4"] { --grid-tc: repeat(4, 1fr) }
r-grid[columns="5"] { --grid-tc: repeat(5, 1fr) }
r-grid[columns="6"] { --grid-tc: repeat(6, 1fr) }
r-grid[columns="7"] { --grid-tc: repeat(7, 1fr) }
r-grid[columns="8"] { --grid-tc: repeat(8, 1fr) }
r-grid[columns="9"] { --grid-tc: repeat(9, 1fr) }
r-grid[columns="10"] { --grid-tc: repeat(10, 1fr) }
r-grid[columns="11"] { --grid-tc: repeat(11, 1fr) }
r-grid[columns="12"] { --grid-tc: repeat(12, 1fr) }

/* span=start... */
r-grid > r-cell[span^="1"] { --grid-cs: 1 }
r-grid > r-cell[span^="2"] { --grid-cs: 2 }
r-grid > r-cell[span^="3"] { --grid-cs: 3 }
r-grid > r-cell[span^="4"] { --grid-cs: 4 }
r-grid > r-cell[span^="5"] { --grid-cs: 5 }
r-grid > r-cell[span^="6"] { --grid-cs: 6 }
r-grid > r-cell[span^="7"] { --grid-cs: 7 }
r-grid > r-cell[span^="8"] { --grid-cs: 8 }
r-grid > r-cell[span^="9"] { --grid-cs: 9 }
r-grid > r-cell[span^="10"] { --grid-cs: 10 }
r-grid > r-cell[span^="11"] { --grid-cs: 11 }
r-grid > r-cell[span^="12"] { --grid-cs: 12 }

/* span=...+width, span=...-end */
r-grid > r-cell[span$="+1"], r-grid > r-cell[span="1"] { --grid-ce: 1 }
r-grid > r-cell[span$="+2"], r-grid > r-cell[span$="-1"], r-grid > r-cell[span="2"] { --grid-ce: 2 }
r-grid > r-cell[span$="+3"], r-grid > r-cell[span$="-2"], r-grid > r-cell[span="3"] { --grid-ce: 3 }
r-grid > r-cell[span$="+4"], r-grid > r-cell[span$="-3"], r-grid > r-cell[span="4"] { --grid-ce: 4 }
r-grid > r-cell[span$="+5"], r-grid > r-cell[span$="-4"], r-grid > r-cell[span="5"] { --grid-ce: 5 }
r-grid > r-cell[span$="+6"], r-grid > r-cell[span$="-5"], r-grid > r-cell[span="6"] { --grid-ce: 6 }
r-grid > r-cell[span$="+7"], r-grid > r-cell[span$="-6"], r-grid > r-cell[span="7"] { --grid-ce: 7 }
r-grid > r-cell[span$="+8"], r-grid > r-cell[span$="-7"], r-grid > r-cell[span="8"] { --grid-ce: 8 }
r-grid > r-cell[span$="+9"], r-grid > r-cell[span$="-8"], r-grid > r-cell[span="9"] { --grid-ce: 9 }
r-grid > r-cell[span$="+10"], r-grid > r-cell[span$="-9"], r-grid > r-cell[span="10"] { --grid-ce: 10 }
r-grid > r-cell[span$="+11"], r-grid > r-cell[span$="-10"], r-grid > r-cell[span="11"] { --grid-ce: 11 }
r-grid > r-cell[span$="+12"], r-grid > r-cell[span$="-11"], r-grid > r-cell[span="12"] { --grid-ce: 12 }
r-grid > r-cell[span$="-12"] { --grid-ce: 13 }

/* connect vars */
r-grid > r-cell[span] { grid-column-end: span var(--grid-ce) }
r-grid > r-cell[span*="+"], r-grid > r-cell[span*="-"], r-grid > r-cell[span*=".."] {
  grid-column-start: var(--grid-cs) }
r-grid > r-cell[span*="-"], r-grid > r-cell[span*=".."] {
  grid-column-end: var(--grid-ce) }
r-grid > r-cell[span="row"] { grid-column: 1 / -1 }

/* for window width <= 768 */
@media only screen and (max-width: 768px) {
  r-grid[columns-s="1"] { --grid-tc: repeat(1, 1fr) }
  r-grid[columns-s="2"] { --grid-tc: repeat(2, 1fr) }
  r-grid[columns-s="3"] { --grid-tc: repeat(3, 1fr) }
  r-grid[columns-s="4"] { --grid-tc: repeat(4, 1fr) }
  r-grid[columns-s="5"] { --grid-tc: repeat(5, 1fr) }
  r-grid[columns-s="6"] { --grid-tc: repeat(6, 1fr) }
  r-grid[columns-s="7"] { --grid-tc: repeat(7, 1fr) }
  r-grid[columns-s="8"] { --grid-tc: repeat(8, 1fr) }
  r-grid[columns-s="9"] { --grid-tc: repeat(9, 1fr) }
  r-grid[columns-s="10"] { --grid-tc: repeat(10, 1fr) }
  r-grid[columns-s="11"] { --grid-tc: repeat(11, 1fr) }
  r-grid[columns-s="12"] { --grid-tc: repeat(12, 1fr) }
  
  /* span-s=start... */
  r-grid > r-cell[span-s^="1"] { --grid-cs: 1 }
  r-grid > r-cell[span-s^="2"] { --grid-cs: 2 }
  r-grid > r-cell[span-s^="3"] { --grid-cs: 3 }
  r-grid > r-cell[span-s^="4"] { --grid-cs: 4 }
  r-grid > r-cell[span-s^="5"] { --grid-cs: 5 }
  r-grid > r-cell[span-s^="6"] { --grid-cs: 6 }
  r-grid > r-cell[span-s^="7"] { --grid-cs: 7 }
  r-grid > r-cell[span-s^="8"] { --grid-cs: 8 }
  r-grid > r-cell[span-s^="9"] { --grid-cs: 9 }
  r-grid > r-cell[span-s^="10"] { --grid-cs: 10 }
  r-grid > r-cell[span-s^="11"] { --grid-cs: 11 }
  r-grid > r-cell[span-s^="12"] { --grid-cs: 12 }
  
  /* span-s=...+width, span-s=...-end */
  r-grid > r-cell[span-s$="+1"], r-grid > r-cell[span-s="1"] { --grid-ce: 1 }
  r-grid > r-cell[span-s$="+2"], r-grid > r-cell[span-s$="-1"], r-grid > r-cell[span-s="2"] { --grid-ce: 2 }
  r-grid > r-cell[span-s$="+3"], r-grid > r-cell[span-s$="-2"], r-grid > r-cell[span-s="3"] { --grid-ce: 3 }
  r-grid > r-cell[span-s$="+4"], r-grid > r-cell[span-s$="-3"], r-grid > r-cell[span-s="4"] { --grid-ce: 4 }
  r-grid > r-cell[span-s$="+5"], r-grid > r-cell[span-s$="-4"], r-grid > r-cell[span-s="5"] { --grid-ce: 5 }
  r-grid > r-cell[span-s$="+6"], r-grid > r-cell[span-s$="-5"], r-grid > r-cell[span-s="6"] { --grid-ce: 6 }
  r-grid > r-cell[span-s$="+7"], r-grid > r-cell[span-s$="-6"], r-grid > r-cell[span-s="7"] { --grid-ce: 7 }
  r-grid > r-cell[span-s$="+8"], r-grid > r-cell[span-s$="-7"], r-grid > r-cell[span-s="8"] { --grid-ce: 8 }
  r-grid > r-cell[span-s$="+9"], r-grid > r-cell[span-s$="-8"], r-grid > r-cell[span-s="9"] { --grid-ce: 9 }
  r-grid > r-cell[span-s$="+10"], r-grid > r-cell[span-s$="-9"], r-grid > r-cell[span-s="10"] { --grid-ce: 10 }
  r-grid > r-cell[span-s$="+11"], r-grid > r-cell[span-s$="-10"], r-grid > r-cell[span-s="11"] { --grid-ce: 11 }
  r-grid > r-cell[span-s$="+12"], r-grid > r-cell[span-s$="-11"], r-grid > r-cell[span-s="12"] { --grid-ce: 12 }
  r-grid > r-cell[span-s$="-12"] { --grid-ce: 13 }
  
  /* connect vars */
  r-grid > r-cell[span-s] { grid-column-end: span var(--grid-ce) }
  r-grid > r-cell[span-s*="+"], r-grid > r-cell[span-s*="-"], r-grid > r-cell[span-s*=".."] {
    grid-column-start: var(--grid-cs) }
  r-grid > r-cell[span-s*="-"], r-grid > r-cell[span-s*=".."] {
    grid-column-end: var(--grid-ce) }
  r-grid > r-cell[span-s="row"] { grid-column: 1 / -1 }
}

/* for window width >= 1600 */
@media only screen and (min-width: 1599px) {
  r-grid[columns-l="1"] { --grid-tc: repeat(1, 1fr) }
  r-grid[columns-l="2"] { --grid-tc: repeat(2, 1fr) }
  r-grid[columns-l="3"] { --grid-tc: repeat(3, 1fr) }
  r-grid[columns-l="4"] { --grid-tc: repeat(4, 1fr) }
  r-grid[columns-l="5"] { --grid-tc: repeat(5, 1fr) }
  r-grid[columns-l="6"] { --grid-tc: repeat(6, 1fr) }
  r-grid[columns-l="7"] { --grid-tc: repeat(7, 1fr) }
  r-grid[columns-l="8"] { --grid-tc: repeat(8, 1fr) }
  r-grid[columns-l="9"] { --grid-tc: repeat(9, 1fr) }
  r-grid[columns-l="10"] { --grid-tc: repeat(10, 1fr) }
  r-grid[columns-l="11"] { --grid-tc: repeat(11, 1fr) }
  r-grid[columns-l="12"] { --grid-tc: repeat(12, 1fr) }
  
  /* span-l=start... */
  r-grid > r-cell[span-l^="1"] { --grid-cs: 1 }
  r-grid > r-cell[span-l^="2"] { --grid-cs: 2 }
  r-grid > r-cell[span-l^="3"] { --grid-cs: 3 }
  r-grid > r-cell[span-l^="4"] { --grid-cs: 4 }
  r-grid > r-cell[span-l^="5"] { --grid-cs: 5 }
  r-grid > r-cell[span-l^="6"] { --grid-cs: 6 }
  r-grid > r-cell[span-l^="7"] { --grid-cs: 7 }
  r-grid > r-cell[span-l^="8"] { --grid-cs: 8 }
  r-grid > r-cell[span-l^="9"] { --grid-cs: 9 }
  r-grid > r-cell[span-l^="10"] { --grid-cs: 10 }
  r-grid > r-cell[span-l^="11"] { --grid-cs: 11 }
  r-grid > r-cell[span-l^="12"] { --grid-cs: 12 }
  
  /* span-l=...+width, span-l=...-end */
  r-grid > r-cell[span-l$="+1"], r-grid > r-cell[span-l="1"] { --grid-ce: 1 }
  r-grid > r-cell[span-l$="+2"], r-grid > r-cell[span-l$="-1"], r-grid > r-cell[span-l="2"] { --grid-ce: 2 }
  r-grid > r-cell[span-l$="+3"], r-grid > r-cell[span-l$="-2"], r-grid > r-cell[span-l="3"] { --grid-ce: 3 }
  r-grid > r-cell[span-l$="+4"], r-grid > r-cell[span-l$="-3"], r-grid > r-cell[span-l="4"] { --grid-ce: 4 }
  r-grid > r-cell[span-l$="+5"], r-grid > r-cell[span-l$="-4"], r-grid > r-cell[span-l="5"] { --grid-ce: 5 }
  r-grid > r-cell[span-l$="+6"], r-grid > r-cell[span-l$="-5"], r-grid > r-cell[span-l="6"] { --grid-ce: 6 }
  r-grid > r-cell[span-l$="+7"], r-grid > r-cell[span-l$="-6"], r-grid > r-cell[span-l="7"] { --grid-ce: 7 }
  r-grid > r-cell[span-l$="+8"], r-grid > r-cell[span-l$="-7"], r-grid > r-cell[span-l="8"] { --grid-ce: 8 }
  r-grid > r-cell[span-l$="+9"], r-grid > r-cell[span-l$="-8"], r-grid > r-cell[span-l="9"] { --grid-ce: 9 }
  r-grid > r-cell[span-l$="+10"], r-grid > r-cell[span-l$="-9"], r-grid > r-cell[span-l="10"] { --grid-ce: 10 }
  r-grid > r-cell[span-l$="+11"], r-grid > r-cell[span-l$="-10"], r-grid > r-cell[span-l="11"] { --grid-ce: 11 }
  r-grid > r-cell[span-l$="+12"], r-grid > r-cell[span-l$="-11"], r-grid > r-cell[span-l="12"] { --grid-ce: 12 }
  r-grid > r-cell[span-l$="-12"] { --grid-ce: 13 }
  
  /* connect vars */
  r-grid > r-cell[span-l] { grid-column-end: span var(--grid-ce) }
  r-grid > r-cell[span-l*="+"], r-grid > r-cell[span-l*="-"], r-grid > r-cell[span-l*=".."] {
    grid-column-start: var(--grid-cs) }
  r-grid > r-cell[span-l*="-"], r-grid > r-cell[span-l*=".."] {
    grid-column-end: var(--grid-ce) }
  r-grid > r-cell[span-l="row"] { grid-column: 1 / -1 }
}

/* .debug can be added to a r-grid to visualize its effective cells */
r-grid.debug > * {
  --color: rgba(248,110,91 ,0.3);
  background-image:
    linear-gradient(to bottom, var(--color) 0%, var(--color) 100%);
}
r-grid.debug > :nth-child(6n+2) { --color: rgba(103,126,208,0.3) }
r-grid.debug > :nth-child(6n+3) { --color: rgba(224,174,72 ,0.3) }
r-grid.debug > :nth-child(6n+4) { --color: rgba(77, 214,115,0.3) }
r-grid.debug > :nth-child(6n+5) { --color: rgba(217,103,219,0.3) }
r-grid.debug > :nth-child(6n+6) { --color: rgba(94, 204,211,0.3) }
r-grid.debug > :nth-child(6n+7) { --color: rgba(248,110,91 ,0.3) }