I'm not keen on constantly being switched back and forth between different weapons when snagging what ought to be real powerups. But other than that, the game does very well, moving fast with nice-looking sprites and all that sort of thing. Easy in the early going, I'm sure it gets tough later on.
It finally starts to get challenging around Areas -6 and -7; -8 is a brutal bubble bombardment (oh those sound effects argh), and -9, which someone on the internet said is the final stage, is a boss rush that I haven't made it through. ;_; Wikipedia says you get 4 continues. Also apparently the game was named after a Japanese sci-fi action movie that released around the same time in 1989.