While all manner of technique has been employed to try to elevate a game in the shooter genre from the dregs, one of my personal favorites has always been ship modification. Adding new parts to your vessel, or having it morph into any number of different shapes is an intriguing tactic that I've seen all too rarely, let alone while remaining any kind of fun factor. Tenseiryu: Saint Dragon uses an interesting device that I think pays off as far as finding a balance between fun and innovation.
You have no real plot to speak of, but you do have the opportunity to pilot a dragon, something I feel should have been used much more (Dragon Spirit Forever!). This particular dragon is comprised of circular segments; several segments in all. The interesting device in this game has to do with maneuvering your dragon around the screen, going backward and forward to move the segments around and avoid taking hits while disposing of the enemies. You contort your dragon in all kinds of compromising positions to eliminate enemies as effectively as is possible. I've found a winning contortion in circling the segments around until you look similar to a sphere with a head. Having to move out of harm's way from this position can be tricky, though, so constantly shifting shapes, as it were, is a must.
As far as gameplay mechanics are concerned, they are probably what you would expect to find in a game of this genre. Collect various power-ups to increase your overall firepower, etc. It is worth note that enemies will occasionally leave the screen right to left, and return from the left and proceed back to the right; large enemies, usually. This adds to the already significant challenge, as you are never sure when enemies you failed to destroy may return.
As far as said firepower is concerned, though, it usually comes far too sparingly, and it can be exceedingly difficult to take out the larger enemies with the inadequate default weapon. Some of the die-hard fans of this genre swear that it only makes their mastery of the default gun something to marvel, but those are the guys who also usually wear their "character" outfit when they role play, and don't know how to talk to girls.
Minor issues aside, this is a game worth looking into. Those brave enough to endure the wrath of Keldor, the Saint Dragon will be rewarded with a plus four battle ax of Gelvar!