Was just mucking around with the new update a bit...
Classic mode is no joke, it's about as difficult as Castlevania 1 for NES and structurally almost identical in design.
I managed to slog through it in about an hour.
There's a save file, so it removes the tedium of starting the entire game over if you run out of lives / continues but it's still obnoxious in it's execution.
I made a simple table.
If you have some skills you can manage to get through it fairly easily. The final boss is annoying but only requires a bit of memorization to get through flawlessly. On my 4th attempt I nailed it without breaking a sweat, just memorize the tells of the final two bosses and you're golden.
I couldn't find the value for health, I messed around with it for about 20 minutes before just giving up. I figured the value was either 16 or 32 for full health but that's not the case at all... not sure how the math is calculated for each bar but it's fucking weird.
I made pointers for both sub weapon energy and lives...
At least this way if things are going poorly you can find a crystal and just "freeze time" through stages... It's especially useful on stages 3 and 4 with a lot of cheap pit fall deaths and strategic enemy placement.
With the lives you can have infinite attempts at a stage as long as you reach a door, that's basically a check point for the stage so you won't have to repeat the entire thing over again, saves a lot of time.
If you lock your sub weapon energy make sure to unlock it at the end of a stage or the game will just stagnate and lock. This hypothetically earns you infinite amounts of score for your weapon energy "left overs" but it will just lock your game infinitely until the value is unlocked... so make sure to alt + tab out and unlock it or set a hotkey for it.