This app lays out tiles based on an underlying square or hexagonal tiling pattern. Specify each tile using a 4 or 6 character string. The characters specify edges of the tiles.
"AaBbCcDd" specify pointy edges. "A" connects to "a", etc.
"EeFf" specify off-center flat edges. "E" connects to "e", etc.
"1234" specify centered flat edges. These can connect to themselves.
"-" is an empty edge, and behaves like a flat edge.
Setting the style to "knotwork" shows tiles with four non-empty edges as two crossing pipes.