/ explode
/ http://www.math.chalmers.se/~magnus/GuiFest-95/challenges.html
/ http://www.cs.chalmers.se/~magnus/GuiFest-95/fudgets/solutions.html
/ http://www.wadham.ox.ac.uk/~ohazell/Atoms/

/ message processing:

."\\r ",$_t                                                   / set random seed to time

offer:{                                                       / offer a game
 S::-1 1()_draw 2                                             / my sign
 N:::[#x;0$_i;6 6]                                            / board dimensions
 B::(*/N)#0                                                   / board, flattened
 A::arcs N 0                                                  / square-to-square arcs
 P::()_draw 2                                                 / play (1) or wait (0)
}

arcs:{[n]                                                     / compute arcs
 m:(-1 0;0 -1;1 0;0 1)+\:/:/:(!n),/:\:!n                      / matrix of neighbors
 ,/{n _sv+x@&((x[;0]>-1)&x[;0]<n)&(x[;1]>-1)&x[;1]<n}''m}     / eliminate out of range

accept:{                                                      / accept a game
 W::3:(`$;0$)@'_i                                             / get handle of opponent
 @[_d;`N`A`B`P`S;:;W 4:_n]                                    / get initial state
}

.m.c:"\\\\"                                                   / exit on close
.m.g:{W::_w;`show$`Z;(N;A;B;~P;-S)}                           / get handle, show board, return initial state
.m.s:{[b]B::b;P::1;Z::N#B}                                    / new board, my turn, update window

:[_p;offer;accept]_i                                          / offer if there is a port

/ game logic:

explode:{[b;i]:[*full[b;i];last/next\b;b]}                    / resolve board if move filled a square

next:{[b]                                                     / next state of board
 i:&mine[b;I]&full[b;I]                                       / where i'm full
 j:(?,/A i)_dvl i                                             / arcs from those squares
 b:@[b;j@&k:full[b;j];-:]                                     / make your full squares mine
 b:@[b;j@&~k;S*1+__abs]                                       / increment remaining squares
 @[b;i;:;0]}                                                  / zero out where i'm full

last:{[b;c]@[c;i;:;S*C i:&mine[b;I]&full[b;I]]}               / fill where previously full
 
mine:{[b;i]S=sign b i}                                        / squares i occupy
full:{[b;i]C[i]=_abs b i}                                     / squares which are full
sign:{(-x<0)+0<x}                                             / sign (0 or 1 or -1)
ok:{(~x)|S=sign x}                                            / not occupied by opponent

/ gui:

O..d:"{:[1<#x;0;*x]}@?sign B"                                 / game over (1 or -1) or not (0)
I:!*/N                                                        / indices of flattened board
C:#:'A                                                        / counts of arcs
D:_ci 164                                                     / stone character
Z:N#0                                                         / window

Z..k:"if[P&*ok B N _sv _i                                     / click: if i can move ...
       B[N _sv _i]+:S                                         / update board
       Z:N#B:explode[B;N _sv _i]                              / process board, update window
       P:0                                                    / turn me off
       W 3:B]"                                                / notify opponent

Z..f:{-4$(__abs x)#D}                                         / square format

anno:{[o]                                                     / annotate window:
 :[o;"game over: ",($`red`green)[o=1]," wins"                 / if game over, say who won
  ($`stop`go)[P],": you are ",($`red`green)S=1]}              / else say identity, who moves

Z..l..d:".k.anno .k.O"                                        / annotation depends on game-state

Z..bg:{                                                       / square background
 :[*full[B;i:N _sv _i];990000 9900@1=sign B i                 / if full, red or green
   ok B i;999900                                              / else if ok to move, yellow
   808080]}                                                   / else gray

Z..kl:"`show$`H"                                              / get help

H:("k explode                                              "
   ""
   "to offer a game:  k explode -i <port> {rows cols}      "
   "to accept a game:  k explode <machine> <port>          "
   ""
   "you may move when your board says 'go'                 "
   ""
   "background colors:                                     "
   ""
   "  yellow:  you may place a stone here                  "
   "    gray:  you may not place a stone here              "
   "   green:  owned by green                              "
   "     red:  owned by red                                "
   ""
   "the game is over when the board is all red or all green")

if[~_p;`show$`Z]                                              / show board if no port