/**
 * Top (=8) | Right (=4) | Bottom (=2) | Left (=1) bitmask value
 * 0000  ' '  0   ....  = empty
 * 0001  '╴'  1   ...L
 * 0010  '╷'  2   ...B
 * 0011  '┐'  3   ..BL
 * 0100  '╶'  4   .R..
 * 0101  '─'  5   .R.L  = hoizontal
 * 0110  '┌'  6   .RB.
 * 0111  '┬'  7   .RBL
 * 1000  '╵'  8   T...
 * 1001  '┘'  9   T..L
 * 1010  '│'  10  T.B.  = vertical
 * 1011  '┤'  11  T.BL
 * 1100  '└'  12  TR..
 * 1101  '┴'  13  TR.L
 * 1110  '├'  14  TRB.
 * 1111  '┼'  15  TRBL  = crossing
 */
export type TRBL = 0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15;