Crypt of the Necrodancer has a deterministic, editable replay format. Therefore it is possible to make TASes of the game (albeit slowly).
A TAS got released today of probably the hardest imaginable speedrun category. Coda is the hardest character, unable to upgrade from a dagger, dying in one hit, dying if you ever make an invalid move/lose your combo, dying if you pick up gold and moving at double the speed of the music. The TASer (@Teraka91 on Twitter) controls two Codas at once using the same input to beat the game in under 4 minutes while satisfying low% condition (never picking up an item or using a shrine). It's recommended that you watch at 0.5x or even 0.25x speed to be able to follow it, because it is extremely fast.
Link to video
This is one of my favourite shmups, so I just want to say I'm rooting for you :D Playing on very hard will be a very interesting stylistic choice. Though you could go all out by playing in white label (which is considered to be harder than black label), black label is much easier to get huge chains in, and since the goal is to get a massive score it's acceptable to me.
EDIT: TO contribute, here are the world records for Dodonpachi DaiOuJou Black Label.
First, with Type A, by HFD, 3.5 billion:
Link to video
Second, with Type B, also by HFD, 3.3 billion:
Link to video
EDIT 2: Thought of some things on the way home, probably stuff you already know to look for though :0
Your laser has an 'aura' which is a small, damaging rectangle around your ship. It builds hyper meter and damage very fast IIRC. Pro players use the aura on things that are invincible due to being at the top of the screen - or because they were left alive, because they become invincible due to being at the BOTTOM of the screen, too. Maybe there are opportunities to aura things at the top and bottom of the screen that pro players leave out due to being inconsistent or unknown.
With three different weapons (shot, laser, aura) I was wondering if there are weird combinations of the three that extract more or less points/combos/hyper meters from enemies. Bosses, too - the pods of boss 1, the falling guns of boss 3 final attack, the falling casings of stage 4's midboss, the options and discs of boss 4, the midboss of 5 that spews discs - can you take advantage of these by auraing (or otherwise) in ways pro players don't?
(btw, did you compare 'auraing the stage 1 midboss and never moving off it' to what you do in the TAS, which is go back to grab the tanks?)
It's also interesting that delaying things in weird ways (killing blows, bee pickups) will give extra points due to the multiplier being higher.
I believe there's a bonus for having maximum bombs that is given out per frame and increases every time you get another bomb - so I think getting bombs earlier will be a marginal scoring advantage.
Have you tried turning on 'C is Autofire' in the operator menu, and alternating A and C? Maybe you can get a 60Hz hyper shot.
Does moving diagonally shrink your hitbox? (It does in some other Cave games, like SaiDaiOuJou (AFAIK), so it's worth testing.)
Here's a guide on how Hyper Rank works in DoJBL: https://www.dropbox.com/s/n8z15uu28w2tath/dojbl_guide.pdf?dl=0
Chaining mechanics explained: http://shmups.system11.org/viewtopic.php?p=315284#p315284
More up-to-date documentation related to score, using HFD's run as a reference: http://shmups.system11.org/viewtopic.php?p=777219#p777219
A known improvement to HFD's world record: http://shmups.system11.org/viewtopic.php?p=827392#p827392 + http://shmups.system11.org/viewtopic.php?p=827634#p827634http://shmups.system11.org/viewtopic.php?p=695296#p695296 'BTW using shot on popcorns increases your hyper bar way faster than lasering them'
And just for fun, a video of DaiOuJou White Label that includes a full chain of 1-3, which was thought to only be possible on Black Label, but is actually just extremely difficult: https://www.youtube.com/watch?v=mlzixxnGm0w&t=6m29s
To me, making a 1st loop only TAS of a ghost and goblins series game is like TASing pokemon gold and stopping when you beat the elite four. But ultimately it's up to the TASer.
