diff --git a/assignment1-18/chess b/assignment1-18/chess
deleted file mode 100755
index 042241c..0000000
Binary files a/assignment1-18/chess and /dev/null differ
diff --git a/assignment1-18/chessboard.c b/assignment1-18/chessboard.c
index ae8e258..3993239 100644
--- a/assignment1-18/chessboard.c
+++ b/assignment1-18/chessboard.c
@@ -298,6 +298,7 @@ bool player_checks(struct chessboard *cb, enum player p) {
 
 bool player_checkmates(struct chessboard *cb, enum player p) {
     int i, j;
+    // for every opponent's piece
     for (i = 0; i < 8; i++) {
         for (j = 0; j < 8; j++) {
             if (is_empty(cb, i, j) || player(cb, i, j) == p) {
@@ -305,6 +306,9 @@ bool player_checkmates(struct chessboard *cb, enum player p) {
             }
 
             int k, l;
+            // for every possible position not equal to the current position of
+            // that piece, which is empty or occupied by our pieces (implying
+            // capture)
             for (k = 0; k < 8; k++) {
                 for (l = 0; l < 8; l++) {
                     if ((k == i && l == j) ||
@@ -313,16 +317,20 @@ bool player_checkmates(struct chessboard *cb, enum player p) {
                         continue;
                     }
 
+                    // check if the move is valid
                     bool can = can_move(cb, p == BLACK ? WHITE : BLACK,
                             i, j, k, l);
+                    // if not, carry on
                     if (!can) {
                         continue;
                     }
 
+                    // if valid, perform the move and check for check.
                     enum pieces tmp = cb_move(cb, i, j, k, l);
                     bool check = player_checks(cb, p);
                     cb_move_restore(cb, tmp, i, j, k, l);
 
+                    // if check is no longer there, then this is not a checkmate
                     if (!check) {
                         return false;
                     }
@@ -331,6 +339,7 @@ bool player_checkmates(struct chessboard *cb, enum player p) {
         }
     }
 
+    // if no such move exists, then this is checkmate
     return true;
 }
 
@@ -380,13 +389,15 @@ enum mstatus move(
         return INVALID;
     }
 
+    // check if we are currently in check state
     bool check_before = player_checks(cb, p == WHITE ? BLACK : WHITE);
+    // determine if move is valid
     bool can = can_move(cb, p, from_row, from_col, to_row, to_col);
 
     if (!can) {
         return INVALID;
     } else {
-        // FIXME: check if move is allowed in check state
+        // try to move, and revert if invalid due to check in progress
         enum pieces tmp = cb_move(cb, from_row, from_col, to_row, to_col);
         if (player_checks(cb, p == WHITE ? BLACK : WHITE) && check_before) {
             DEBUG("move: move does not end check state, invalid");