Animal Chess

Try to enter the opponent's cave and become the king of beasts!

Changelog v0.1:

You can play with your friend on the same computer in this version.

Simple rules are as follows: 

*when one of your animals arrives the opponent's cave, you win

*rat<cat<dog<wolf<leopard<tiger<lion<elephant<rat

*caught in the opponent's trap, your animal becomes the weakest

*only rat can get into the river

*tigers and lions can jump over the river when no rats hindering

*a rat cannot beat elephants or another rat when entering or exiting the river

Plans for further versions:

*add online versus function and man-machine versus AI

*make repenting feasible

*consider forbidden moves 

I'll appreciate if any bugs pointed out.