diff --git a/ArduChess.ino b/ArduChess.ino
index 335e21e..75ccde2 100644
--- a/ArduChess.ino
+++ b/ArduChess.ino
@@ -12,6 +12,7 @@ void setup() {
 	Board::init();
 	Serial.begin(115200);
 	pinMode(LED_BUILTIN, OUTPUT);
+	//debug_check();
 	//perft_test();
 	//bench();
 }
diff --git a/Tasks.h b/Tasks.h
index 7e1ac07..441bbd3 100644
--- a/Tasks.h
+++ b/Tasks.h
@@ -31,27 +31,39 @@ unsigned long pseudo_perft(byte depth) {
 	return move_count;
 }
 
-unsigned long divide(byte depth) {
-	// only checks pseudolegality
-	// but, it should work overall
+unsigned long perft(byte depth) {
 	if(depth == 0) return 1;
-	if(depth == 3) blink();
+	if(depth == 2) blink();
 	unsigned long move_count = 0;
 	Movegen gen;
 	Move m;
 
-	while (true) {
-		m = gen.next_move();
+	while((m = gen.next_move()).sq_to != 255) {
+		if(make_safe(m)) {
+			move_count += perft(depth-1);
+			Board::unmake();
+		}
+	}
+	return move_count;
+}
+
+unsigned long divide(byte depth) {
+	// only checks pseudolegality
+	// but, it should work overall
+	if(depth == 0) return 1;
+	if(depth == 2) blink();
+	unsigned long move_count = 0;
+	Movegen gen;
+	Move m;
+
+	while((m = gen.next_move()).sq_to != 255){
 		print_move(m);
 		Serial.print(F(" "));
-		if(m.sq_to != 255) {
-			Board::make(m);
-			int count = pseudo_perft(depth-1);
+		if(make_safe(m)) {
+			unsigned long count = perft(depth-1);
 			Serial.println(count);
 			move_count += count;
 			Board::unmake();
-		} else {
-			break;
 		}
 	}
 	return move_count;
@@ -114,7 +126,20 @@ void debug_check() {
 	Board::make({0x05, 0x41, P_EMPTY});
 	Board::print();
 
-	Serial.println(Threat::is_check());
+	Serial.print(Threat::is_check());
+	Serial.println(Threat::illegal());
+
+	divide(1);
+
+	Board::make({0x60, 0x40, P_EMPTY});
+	Board::print();
+	Serial.print(Threat::is_check());
+	Serial.println(Threat::illegal());
+
+	Board::unmake();
+	Board::unmake();
+	Board::unmake();
+	Board::unmake();
 }
 
 void debug_ep() {
diff --git a/Threat.h b/Threat.h
index f5c39fc..68939b7 100644
--- a/Threat.h
+++ b/Threat.h
@@ -5,7 +5,6 @@ namespace Threat {
 	byte can_capture(byte square) {
 		// TODO make this more efficient
 		byte t = 0;
-		Board::swap_side();
 		Movegen gen = Movegen();
 		Move m;
 		while((m = gen.next_move()).sq_to != 255) {
@@ -13,7 +12,6 @@ namespace Threat {
 				t++;
 			}
 		}
-		Board::swap_side();
 		return t;
 	}
 
@@ -39,4 +37,23 @@ namespace Threat {
 	
 }
 
+bool make_safe(Move m) {
+	byte sq_diff = m.sq_to - m.sq_from;
+	if(m.sq_from == Board::field[PTR_W_KING | Board::black_moving()] &&
+	   abs(sq_diff) == 2
+	  ) {
+		// we are castling, so check if we are threatened in the square the king moves through
+		byte sq = m.sq_from + (sq_diff/2);
+		if(Threat::is_check() || Threat::threats(sq) > 0) {
+			return false; // castle blocked; return failure
+		}
+	}
+	Board::make(m);
+	if(Threat::illegal()) {
+		Board::unmake();
+		return false;
+	}
+	return true;
+}
+
 #endif
\ No newline at end of file
diff --git a/Types.h b/Types.h
index ee7acb6..d6a493d 100644
--- a/Types.h
+++ b/Types.h
@@ -61,7 +61,7 @@ void print_move(Move m) {
 	}
 	print_sq(m.sq_from);
 	print_sq(m.sq_to);
-	byte pc = m.pc_prom & 0x7;
+	Piece pc = (Piece)(m.pc_prom & 0x7);
 	if(pc != 0) Serial.print(piece_to_char(pc));
 }