www.jap-sai.com - Ozma Wars

Ozma Wars is mainly of interest for being one of SNK's very first releases, appearing in December 1979. It remains an interesting historical landmark of sorts, not only as a super-vintage SNK production but also as an innovative twist on the staple 'invader' formula of the late 70s.
While directly based on Space Invaders (1978) and Galaxian (1979) the game stood out by presenting a multitude of different stages, enemy formations and events instead of the usual single-screen setup. Also, the player does not have a stock of 'lives' - instead the game's longevity is managed by a numerical energy reserve at the bottom left of the screen, that slowly depletes during the course of the game and gets seriously reduced if the ship takes a hit. This energy is refilled every 5 stages or so during a brief 'docking' sequence.
To their credit, SNK did quite well considering this is very first 'invader' effort. It is an exceptionally early game: in 1979, video games were still in their infancy - simplistic game play and questionable collision detection was the norm. Directly compared to the vast majority of other titles of its era it is perfectly acceptable.
But be warned: playing it in retrospective, the glitchy and sluggish animation can be a real a nuisance to deal with, and the oncoming enemies are real tricky to adjust effectively. Not only that - often they disappear, flicker, and then reappear... That might explain why the US release was re-titled 'Space Phantoms'.