sS renderLineCompedSingleLevels(LineCompedSingle<Char> lc) {
  // each byte is the character's "color"
  // (0 for empty, 1 for color one, 2 for color two)
  byte[][] rows = renderLineCompedSingleLevels_raw(lc);
  S text = uncompressLineCompedSingle(lc);
  //printVars(+rows);
  int n = l(first(rows));
  ret lines(map(rows, row -> {
    StringBuilder buf = new(n);
    for i to n: {
      if (row[i] == 0) 
        buf.append(i == n-1 ? " " : "  ");
      else {
        buf.append(text.charAt(i));
        if (i < n-1)
          buf.append(row[i+1] != 0 && row[i+1] != row[i]
            ? '|' : ' ');
      }
    }
    ret str(buf);
  }));
}