diff -r 4d030da07c88 -r 3ab0c2e1a4e2 src/chess/king.c
--- a/src/chess/king.c	Tue Apr 01 10:28:08 2014 +0200
+++ b/src/chess/king.c	Tue Apr 01 12:30:25 2014 +0200
@@ -29,18 +29,88 @@
 
 #include "rules.h"
 #include "king.h"
+#include <stdlib.h>
 
-_Bool king_chkrules(GameState *gamestate, Move* move) {
-    // TODO: implement
+static _Bool king_castling_chkmoved(GameState *gamestate,
+    uint8_t row, uint8_t file) {
+    
+    MoveList *ml = gamestate->movelist;
+    while (ml) {
+        if (ml->move.fromfile == file && ml->move.fromrow == row) {
+            return 1;
+        }
+        ml = ml->next;
+    }
+    
     return 0;
 }
 
+_Bool king_chkrules(GameState *gamestate, Move* move) {
+    if (abs(move->torow - move->fromrow) <= 1 &&
+        abs(move->tofile - move->fromfile) <= 1) {
+        return 1;
+    } else {
+        /* castling */
+        if (move->fromrow == move->torow &&
+            move->fromrow == ((move->piece&COLOR_MASK) == WHITE ? 0 : 7) &&
+            move->fromfile == fileidx('e') &&
+            (move->tofile == fileidx('c') || move->tofile == fileidx('g'))) {
+            
+            return !king_castling_chkmoved(gamestate,
+                move->fromrow, move->fromfile) &&
+                !king_castling_chkmoved(gamestate, move->fromrow,
+                move->tofile == fileidx('c') ? 0 : 7);
+        } else {
+            return 0;
+        }
+    }
+}
+
 _Bool king_isblocked(GameState *gamestate, Move *move) {
-    // TODO: implement
-    return 1;
+    
+    uint8_t opponent_color = opponent_color(move->piece&COLOR_MASK);
+    _Bool blocked = is_covered(gamestate, move->torow, move->tofile,
+        opponent_color);
+    
+    if (abs(move->tofile - move->fromfile) == 2) {
+        if (move->tofile == fileidx('c')) {
+            blocked |= gamestate->board[move->torow][fileidx('b')];
+        }
+        uint8_t midfile = (move->tofile+move->fromfile)/2;
+        blocked |= gamestate->lastmove->move.check ||
+            gamestate->board[move->torow][midfile] ||
+            is_covered(gamestate, move->torow, midfile, opponent_color);
+    }
+    
+    return blocked;
 }
 
 int king_getlocation(GameState *gamestate, Move *move) {
-    // TODO: implement
-    return INVALID_MOVE_SYNTAX;
+    
+    uint8_t file, row;
+    
+    for (int f = -1 ; f <= 1 ; f++) {
+        for (int r = -1 ; r <= 1 ; r++) {
+            if (f == 0 && r == 0) {
+                continue;
+            }
+            file = move->tofile + f;
+            row = move->torow + r;
+            if (isidx(file) && isidx(row)) {
+                if (gamestate->board[row][file] == move->piece) {
+                    if ((move->fromfile != POS_UNSPECIFIED
+                        && move->fromfile != file) ||
+                        (move->fromrow != POS_UNSPECIFIED
+                        && move->fromrow != row)) {
+                        return INVALID_POSITION;
+                    }
+                    move->fromfile = file;
+                    move->fromrow = row;
+                    return VALID_MOVE_SYNTAX;
+                }
+            }
+        }
+    }
+    
+    return INVALID_POSITION;
 }