Aw yeah, this one Rocks! Varth is one of the best shmups ever! The music, the art, the level design, the boss design, all excellent! And best of all, you can now pause it. You can even Save your progress for later. And you probably should! Because it's got 30 stages and it is very long. How long? On easiest, where everything takes the least damage to destroy, it takes about an hour to fully clear the game. And it only takes longer on higher difficulties since everything takes more damage, including things that probably shouldn't. Though honestly you should consider raising the difficulty by 1 or so, but 3 seemed a bit excessive to me. YMMV But at no point does this game feel like a slog. Not even a little. I even played it more than once to compare the total play time between difficulties and it still feels good to play it. (Which is impressive since I struggle to enjoy games more than once most of the time.)
So yeah, don't hesitate to use the Save and Load feature if you need to. This game may be pretty long, but this masterpiece is worth it!