Great game.. I really enjoy these types of games and the concept is very great as well.. The only thing i could say is it lacks enemy variety.. and could you make it so that the map gets bigger as the game progresses and multiple blue squares can be present at once so that reaching a high score feels more progressive and makes the game even more intense the higher your score is..
That's all i could say, It is already a great game as it is. Keep up the great work man!