Hi Hijong,
Awesome Defender remake. Just writing to report a small bug I encountered in the current version (1.6.5). If you rebind the controls (using a controller), it asks to you press the buttons for "Fire", "Bomb", "Special", "Thrust", "Reverse", and "Pause". However, the buttons it ASKS you to bind and the buttons it ACTUALLY binds are different. I believe it swaps the thrust and reverse buttons with the bomb and special buttons. I was able to figure out a workaround, but this is a bug worth fixing. Cheers!