She may use sprites from Scarlet Weather Rhapsody, but she plays nothing like said game. In fact, all of her moves and gameplay are custom, and spellcards are nowhere to be found. Sakuya doesn't seem to need them after learning a thing or two from Shiki Nanaya and Dio Brando.
Sakuya's gameplay isn't based off any existing Touhou Project fighting games, instead going for a custom style (possibly influenced by Melty Blood) found in Kohaku's other Touhou Project characters. All three punch buttons are Sakuya's Basic Attacks, (B) and (C) summon Shiki Nanaya and Reisen Udongein Inaba as strikers respectively, and (A) is to Shield if it was selected at the beginning of the round.
While most Touhou Project characters place heavy emphasis on projectiles, Sakuya is much more melee oriented, possibly to make her more balanced. Before the battle begins, Sakuya is able to choose between Shielding, Just Defend, and a Parry.
In terms of A.I., Sakuya is similar to the creator's other characters in that she uses M.U.G.E.N's default A.I., making her a rather unchallenging opponent. There is an A.I. patch available, though.
Sakuya has a 12th pallete mode. It doesn't make her cheap, but she gets Road Roller Da! as a Hyper and her two strikers are replaced with Dio Brando's stand, The World.
Hovering the mouse cursor over the Command Input icons will display text that refers to the inputs set in M.U.G.E.N's Key Config.
Icons encased in square brackets [ ] require the respective button(s) to be held down. Hovering the mouse cursor over the icon displays the hold duration if applicable.