Here are some suggestion how Marking could be done alternatively (to the MtG way).
- Turning 45 degrees
- Turning 180 degrees
- Putting a marker on it
Marking alternatively
Kind regards and happy coding
Re: Marking alternatively
Yups, those are all good, and some also used in other games. The MTG patent on marking, interesting as it may be, is most likely expired now in any case unless they filed for a new one.