The captureMatrix only looks at the pieces on the origin and destination. For multiple capture it would have to be not a matrix but a multi-dimensional object.
But I did not see that as a problem. In the example you give an adjacent Lion is captured. Under Chu-Shogi rules this would also be allowed. In the current form the rule thus gives the closest approximation to the original Chu-Shogi rules. You can even allow bridge capture, by exempting the caKcabK moves from application of the capture matrix by suffixing those moves with an apostrophy. (No way to still forbid it when bridged by P or GB, though.)
BTW, it is still possible to handle more complex cases by scripting. By defining an xxxTinker() JavaScript routine you can examine the move it is passed as argument, and set the '64' bit of the variable 'kind' to let the move trigger the forced pass (kind |= 64;). Or the '32' bit to make it a prioritized move.
The captureMatrix only looks at the pieces on the origin and destination. For multiple capture it would have to be not a matrix but a multi-dimensional object.
But I did not see that as a problem. In the example you give an adjacent Lion is captured. Under Chu-Shogi rules this would also be allowed. In the current form the rule thus gives the closest approximation to the original Chu-Shogi rules. You can even allow bridge capture, by exempting the caKcabK moves from application of the capture matrix by suffixing those moves with an apostrophy. (No way to still forbid it when bridged by P or GB, though.)
BTW, it is still possible to handle more complex cases by scripting. By defining an xxxTinker() JavaScript routine you can examine the move it is passed as argument, and set the '64' bit of the variable 'kind' to let the move trigger the forced pass (kind |= 64;). Or the '32' bit to make it a prioritized move.