Great little arcade game, loved the 3D feel of it. The theme selection is a nice touch. Hit detection felt spot on and it wasn't bogged down by menus or unneeded UI. Liked the enemy variety and the endless play of it.
The lock-in-place-and-shoot mechanics felt a little weird / clunky to me. It would have felt more fluid for me if you could lock the direction but still allow "strafing." So A button would still lock the shooting direction but the dpad would allow for movement. I am sure there are reasons for your design choice though so take this with a grain of salt.
Overall great entry, loved it.