SFA manages the feat of making a shmup that is both accessible to beginners as well as offering enough challenge on the more harder difficulties to appease core-gamers as well. Instead of choosing a difficulty, you start with the easiest one and only when you beat a level and various objectives (no hits, total enemy annihilation, etc.) do further difficulties get unlocked. Hard and hardest: two more for each stage.
Unlike old-school games, you don’t have to play through the game from start to finish, instead you can select and replay each level at will, though you have to unlock stages first, which gives the game a nice sense of progression. Death also is not a disparagement here, as you can augment your ship’s various systems by buying stuff with the stars you collect each stage (and which you keep even when you die).
Since the system is a bit on the grindy side, you often find yourself replaying stages again and again to get more dough to buy the next upgrade here or there. And the beauty of it is, this repeated practice will make you a much better player, without demotivating you like a lot of the more old-school shmups do, where you have to replay right from the beginning again and again without any feeling of progression.