Maxim chess

This variant was invented by my younger brother Maxim (9 years). He don't know chess variants, but know that i like to invent them.
He is very new at chess, and his purpose for changing the movement of knight was it's complicated move, so he made the move, he could understand better. It appeared to be quite interesting piece, having some feeling of both Arabian dababah and Chinese cannon.
Otherwise, variant was inspired by "Portal" videogame series, and features teleporting element.
Originally, i was suggesting him to play "Portal chess" to interest him in chess (i'm currently thinking about my game with portals), but he has made up his own version.
Personally i'm interested in chess variants, invented by children, as Demian Freeling, Joshua Nelson and Timothy Newton. They may have some flaws in playability, but contain nice ideas because of non-stereotipical thinking, and it's interesting to see chess from childrens' point of view. And i'm happy that my brother makes his contribution.

Setup

Setup is mostly as in standart chess, but bishops takes places of rook pawns, while two pawns takes places of bishops.

rnpqkpnr
bppppppb
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BPPPPPPB
RNPQKPNR

Pieces

Pieces are mostly normal, expect for knight.
Insted of normal L-shape leap, it can move one or two (if non-leaping) steps horizontally and vertically. If it leaps over occuppied square, it moves three squares instead. However, if it leaps over two occuppied squares, it still moves three squares, move is not prolonged anymore.

Any pawn can make double step from second rank, but not from first.
There is no promotion. If pawn moves to last rank and don't teleport immediatly, it must be removed from game (this move may be capturing).
See "Rules" for another aspect about pawns.

Rules

Game have two special rules, having big effect on playing: teleportation and and ability of two friendly pieces to occupy one square.

Player may move piece to square, already containing another friendly piece, but not leap over it (if piece is non-leaping, of course). There can't be more than two pieces on same square.
When moving to square, containing two opposing pieces, only one, wich has occuppied this sqare earlier, gets captured, while another piece must be pushed to horizontally or vertiacally adjecent empty square (capturer is to choose). If there are no horizontally or vertically adjecent square, second piece is also captured.
If pawn is occuppying one square with another piece, it moves differently: it may move and capture one square sideways (it "loses it's way").

After making a move (in my brother's original version it was also possible before making a move, but it would give extremely high mobility) player may optionlly declare two squares to be portals (and mark them with a pair of checkers). These squares must be empty, must not contain opponent's portals, and must not be in area, isolated by opponent's pieces (and borders), connected eith orthogonally or diagonally. On further turns, piece of either side, moving into portal, teleports to another portal of same player, and both portals vanishes after this.
One player always have two portals or don't have portals at all. Player may change location of one or both of his portals.

There is no castling.