function [ adj, t1_ij ] = turtle_monotile_adjacency ( )

%*****************************************************************************80
%
%% turtle_monotile_adjacency() returns adjacency information for turtle monotile.
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    18 April 2024
%
%  Author:
%
%    John Burkardt
%
%  Output:
%
%    integer ADJ(16,3): ADJ(I,J) describes the J-th neighbor of the 
%    I-th 30-60-90 triangle.  Neighbor J=1 is across from the 30 degree angle,
%    J=2 from the 60 degree angle, and J=3 from the 90 degree angle.
%
%    integer t1_ij(3,2), the (i,j) vertex coordinates of 30-60-90 triangle #1.
%
  adj = [ ...
    -1, -1,  2; ... % 1
    -1,  3,  1; ... % 2
     5,  2,  4; ... % 3
    15, -1,  3; ... % 4
%
     3, -1, -1; ... % 5
    16,  7,  5; ... % 6
    17,  6,  8; ... % 7
     9, -1,  7; ... % 8
%
     8, -1, 10; ... % 9
    18, 11,  9; ... % 10
    19, 10, 12; ... % 11
    -1, -1, 11; ... % 12
%
    -1, -1, 14; ... % 13
    -1, 15, 13; ... % 14
     4, 14, 16; ... % 15
     6, 17, 15; ... % 16
     7, 16, 18; ... % 17
    10, 19, 17; ... % 18
    11, 18, 20; ... % 19
    -1, -1, 19 ];   % 20

  t1_ij = [ ...
    0,  0; ...
    1,  2; ...
    0,  2 ];

  return
end

