Expansion Chess

It is the first variant of chess created by me. As my another game, Fluidity, it was made for Lichess,  big free chess site with billions of games and tens of thousands moves per second, but its developers don’t need many new lines of code, so I write it here.

I proposed it there because the game has standard setup and pieces.

Rules

Every move must be legal in FIDE rules.
If you have 1 piece on opponent’s half of board after his move, you gain 1 point. More your pieces are there after opponent’s move – more points you gain, i. e. you get 1 point per 1 your expanding piece. 
Points are accumulating, because you get points after each move. You collect them for winning.

You win if:

• You collect 20 or more points, and your opponent can’t collect this number or more than you in the next your move (game ends after opponent's turn).
• Your opponent collects 20 or more, and you immediately collect more than opponent (game ends after next opponent's turn).
• You checkmate opponent’s king.

It’s draw if:

• One player collects 20 or more points, and other player also immediately collects this number of points which is collected by the first player (game ends after next his turn).
• It’s stalemate.
• 10 full moves (20 half-moves, no matter after whose move) without going to gaining zone.
• Player’s time is over but he has 15 more points than opponent.

Last revised by Lev Grigoriev.