It's not an easy game to defend, frankly. A game that combines Danmakukun with the thrill of taking photos. Which means no shooting, and no bombs. Also, you will die frequently.
ZUN said he got the idea for Shoot the Bullet from taking actual photographs of danmaku patterns, and has had the idea since Touhou 6. It's probably the second-most disliked of any of the Windows games, in the Western fanbase at least (Phantasmagoria of Flower View being the most). The most common complaint is that it's danmaku practice at best and rage-inducingly impossible in later stages.
It's clearly not impossible in the literal sense, but there's no denying the game's difficulty. Your sprite moves very quickly, even when focused, which can make for some real white knuckle experiences when facing a swarm of danmaku without any bombs. Having said that, there are many aspects of the gameplay that makes this unique game a pleasure to engage with.
First off, scoring. Although the point of the game is to take photographs of bosses, there are additional points awarded for taking chances on getting closer to the boss, getting multiple bullets in the shot, getting yourself and the boss in the shot, and so on. For those after a high score, there are numerous bonus combinations to draw from.
Second, there's the camera. This weapon serves as both a shooter and a bomb, and can be used defensively as well as offensively. Just like a bomb, it can be used to clear danmaku out of your way. The number of "bombs" is endless, in fact, so long as your camera is fully charged. Holding down focus and shoot simultaneously can fully charge your camera in a matter of seconds. Compare this to how long it can take to regain a bomb used in any other Touhou game. Offensively, instead of continuously firing at or shotgunning a boss, you need only fire a set number of times - only ten or less, actually - into a rather large swath of the gaming screen encompassing the boss. And as with defensive maneuvers, there are many offensive tactics you can use.
Third, there are your lives. They are unlimited. This is merciful, because as said earlier, you will die, many, many times. But you can redo the stage immediately afterwards, as many times as it takes to clear it. This is where a lot of players lose their patience, honestly, but for others it's what makes the game so addictive.
Lastly, I'd add that the game dialogue from Aya is pretty entertaining, if not downright poetic. Additionally, drywall over at Shrinemaiden has published an English patch for the game, freely available for download.
And now, enjoy some danmaku:
(An older version of this article was previously published on my now-defunct LiveJournal.)