Starting position:
0 and -1 denote empty spaces
The empty spaces are always together in bottom left most position.
Solve puzzle by moving spaces to bottom right with the numbers in order.

6 possible directions are symbolized by
 5   0
  \ /
4--*--1
  / \
 3   2
(i.e. 1 = right, 4 = left)

The solutions given are for a starting position of "mirror" as this is
also used in the triangles puzzles on this site.  Solutions for other
starting positions of "CW" and "CCW" solutions may also be available in
breadth first search program for triangles puzzle.  A swap of the last 2
tiles is done if the puzzle is not solvable in starting format.

Corners mode by default, if the corners are trimmed another tile is
added (this puzzle is much harder as parity is preserved).