This is a very creative idea! Having a TD game with NES graphics is a refreshing change of pace! Great job! The music is very catchy.
Just so you know, there is a small stutter that happens every 4-5 seconds, but it is not super noticeable and does not affect gameplay. It happens while the round is ongoing, and not during the purchase phase.
Out of curiosity, how did you set up the targeting for the eagles? Do they go for a random space in their range or is there some sort of priority queue?