Looks good but as a fan of Defender/DropZone/Choplifter/ back in the day, Resogun has some issues for me:
Sound effects: Your weapon sounds really weedy and annoying, a bit irritating. Needs to be a lot beefier and destructive sounding.
Ship control: Seems to have a complete lack of inertia and gravity affecting the ship. This is what made Defender so great, the feel of the ship was so weighty and took real skill to master, but when it clicked it just felt amazing to pilot.
Ship control pt 2: The animation when the ship is reversed looks too slow.
Enemy design: The enemies are too abstract and don't look dangerous at all. Random abstract designs with no real substance.
Boss battles: Severely lacking originality here.
Still an obvious day one, but it doesn't look like HouseMarque have completely understood the appeal of the games that they're borrowing from.