diff --git a/FENTESTS.txt b/FENTESTS.txt
index 796702a..4942414 100644
--- a/FENTESTS.txt
+++ b/FENTESTS.txt
@@ -26,6 +26,9 @@ k7/8/8/1p1p2pP/pPpPp3/P1PpPp2/NBNP1P2/KBB1B3 w - g6 0 1
 # 2 Kings, W/B/ pawns on 7th for promotion
 k4n2/4P3/8/8/8/8/4p3/K4N2 w - - 0 1
 
+# position after 1.e4
+rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq - 0 1
+
 # white castled, and can e.p. on c6 black can castle
 # white is a pawn down
 # white has 35 or 36 moves: P=11 + 1 e.p. N=6+3 B=5+5 R=1 Q=3 K=1 + 1 e.p.
diff --git a/src/chessdefs.h b/src/chessdefs.h
index 9b60a83..084ee82 100644
--- a/src/chessdefs.h
+++ b/src/chessdefs.h
@@ -80,6 +80,12 @@ enum {
 #define SET_BLACK(p)    ((p) |= MASK_COLOR)
 #define SET_COLOR(p, c) (!(c)? SET_WHITE(p): SET_BLACK(p))
 
+/* flip a 0-63 square:
+ * Vertical:   G8 (62) becomes G1 (6)
+ * Horizontal: G8 (62) becomes B8 (57)
+ */
+#define FLIP_V(sq)      ((sq) ^ 56)
+#define FLIP_H(sq)      ((sq) ^ 7)
 /* square_t bits structure : rrrrffff
  * ffff: file
  * rrrr: rank
@@ -98,6 +104,12 @@ typedef unsigned char castle_t;
 #define CASTLE_W        (CASTLE_WK | CASTLE_WQ)   /* 00000011 W castle mask */
 #define CASTLE_B        (CASTLE_BK | CASTLE_BQ)   /* 00001100 B castle mask */
 
+/* game phases
+ */
+#define OPENING    0
+#define MIDDLEGAME 1
+#define ENDGAME    2
+
 /* bitboard
  */
 typedef u64 bitboard_t;