>>695EoSD. Touhou 6 with Flandre and Remilia and whatnot. Not the new remake coming out.
Once you get used to the game without all the extra gimmicks the newer games have, the gimmicks are easier, and arguably more fun rather than overwhelming.
Also it has none of the QOL things. new games have a light or indicator where the boss is at the bottom of the screen so you can stare at your character and dodge while still moving to shoot the boss. EoSD does not have this, so forces you to have more awareness of the whole screen, and therefore can appreciate the beauty of the game and bullet patterns in the future.