Transparent Wave, book updated

As mentioned in a previous post, I have changed Wave to be transparent; just as Wave can optionally interact with other pieces, now they can optionally interact with a Wave, or just ignore its presence. This is done so that interactions are symmetrical; what works for Wave, also works to the Wave.

Obviously, each design choice has its own set of additional ramifications. In this case, consequence is that Wave cannot be pinned any more, since it's transparent, and can be ignored. And consequence of that is that now, when pinned piece is moved, or starts a cascade, it has to be replaced with any other piece, but Wave.

Speaking of symmetrical designs, I was tempted at one point to define Wave as completely transparent, i.e. opponent's pieces wouldn't be able to capture a Wave. I dismissed this design as it would still have to allow for a Wave to activate opponent's Wave (that's the major point of a Wave!), so Wave wouldn't be completely transparent. Even worse, that would allow Waves to move about without ever being in danger, and so it would devolve any variant featuring Waves into A Bigger, Better Classical Chess™, now with additional set of annoying little buggers spoiling all the fun. In short; bad, bad design.

Wave being completely transparent would make sense if no interactions with opponent's pieces are ever allowed. I don't want this, since this too devolves any chess variant into slightly better variation of classical chess. The whole point of Wave, with its ability to allow playing with opponent's pieces, is to turn game-play from static, deterministic affair into a seeping-sands ground, for both players, simultaneously. Obviously, too much sand is too bad, this is why there are several restrictions on what Wave can reach and do. 

For instance, players start with just 2 Waves each; cascading of all material (non-Wave) pieces, except Pyramid, has to be initiated by a Wave. So, even if piece starting a cascade gathered enough momentum, most of the time it won't be able to cascade more than two additional material pieces, without using loop(s), which limits reach of pieces. And the most importantly, each play with opponent's pieces requires own Wave to activate opponent's Wave first. Since it's easier to control positioning of own Waves (compared to opponent's), each player is in a reasonable control of where take-over by the opponent could be made, and which pieces are exposed. In short, possibility to take over opponent's pieces is there, without being too easy to do so.

One other change to the book is inclusion of COPYING, LICENSING files; those clarify what is meant when book is put into a public-domain: 

• book itself, i.e. PDF file is in public-domain
• all texts (TEX files) are in public-domain
• an accompanying picture (JPG, NEF files) is in public-domain
• all generated images (PNG files) are in public-domain
• all source-code is released under GNU GPL v3+ license, covered by separate COPYING, LICENSING files

Transparent Wave is small, but significant change to overall design, and game-play. Similarly, explicit book licensing is also small change, but important to protect availability, and usage of the book. So, I'm updating book, which can be found in usual places. The book was published on October 17, 2022, version is 20221017.032524.