Regarding the game's name

I'm astonished that people seem more preoccupied with the title than with the actual rules and mechanics. I've repeatedly had to explain the reasoning behind this choice, invoking terms and definitions that people either refuse to understand or reject on principle. 

EXPTIME is a strict technical term. In the game's title, it is used not as a formal classification, but as a metaphor and a challenge.

The game's mechanics—mandatory self-erasure upon attack and the mirror setup—create such dense branching of forced variations on the 8x8 board that its complete analysis runs into exponential complexity. In this sense, the game behaves like an EXPTIME-complete problem even on a small board.

The title is a hint at this nature of complexity, not at strict mathematical belonging. This is a game where you wrestle with an exponent, not just play chess. Try to calculate just three moves ahead—and you'll feel why this title emerged here.