Some notes I've collected on Castle in the Sky over the years...
Laputa may be on my short list of great boys' adventures, and I think one of the best things Miyazaki ever did (he cribbed the castle from his earlier Cagliostro and from Grimault's King & Bird, and you can see the flock of pigeons in a film he helped animate, Puss n Boots). I think it's a delight, a perfect chase from beginning to end, wonderful variety (giant aircraft, pirates, steam engines, car chases, train chases, underground caverns, military fortresses, superpowered robots, colored smoke, giant storms, flying islands, and more...) and maybe his most villainous villain ever. Sure I'm aware of the borrowings...but I think they work here the way they once worked for me when I first saw Star Wars, some mumblety mumble years ago: mix and match and charm.
And Swift's story does feature a revolving "levitation stone"--though it is, in fact, a giant magnet that acts against the earth's magnetic field to keep the island suspended (and hence, also ironically, a man who abhorred scientists and science ended up writing one of the world's first pieces of true science fiction--fiction with an element predicated strongly on a scientific principle), not a hypertechnomagical glowing blue thing as in the anime."
I've got a few ideas about that levitation stone. Larry Niven's "The Hole Man" speculates that gravity can be used as a way of communicating, like radio (for one thing, gravity can pass through anything), and hence can be treated as a wave, much like radio waves.
I think that "levitation stone" is something that can warp gravity waves, like a lens; it has the ability to harness gravity to lift objects, generate huge amounts of electrical power (even that gigantic gun we see--what is that, hydrogen in a state of near-fusion or even anti-matter kept temporarily in suspension in an electromagnetic bottle?), and even keep things together--which is why the bottom of Laputa fell apart when the stone left its holding place (the blocks of indestructible material that made up the lower hemisphere were held together by gravity--much like doors can be kept closed by electromagnetic locks).
I'm guessing too that light and heat is a by-product of this gravity-bending property--much like a current passing through a wire willgive off heat, even light (ergo, the light bulb). Could this be the reason, also, that the tree roots were attracted to the levitation stone, probing deep into the castle to where the stone is located? And could the tree, feeding off the stone's power, somehow become so incredibly high it bursts through the roof (if you look closely, you can see the twisted girders round the tree trunk).
The fact that Sheeta and Pazu are able to survive because they are thrust into the roots of the tree is so very powerful. If they had tried to run, it would have ruined it
They didn't run because they had made up their minds to die, give up, abdicate Sheeta's right and authority over Laputa so that no one--not even Muska--can have it, or abuse it. If they survive, it's by sheer luck.
Interesting how Laputa is divided into sections, and each party is interested in a different section according to who they are--the soldiers and the general are interested merely in gold and treasure (the easiest part of the castle to enter and arguably the dullest moment in the movie); Muska is interested in the technological power underneath; the children, who embody Miyazaki's sentiments the closest, focus their attention on the garden above.
It's not accident that the roots have penetrated everywhere, even underneath, where Laputa's engines are located; that's Miyazaki's metaphor in operation. When Laputa has fallen apart it has, in effect, shaken off what's peripheral, unimportant, even evil, and kept (thanks to the tree roots) what is truly important together.
Love Laputa; in a way, it's Miyazaki's repudiation of his own love of flying--what's important is not that crystal at the heart of the castle (flight), but the tree with roots holding the whole thing together (groundedness). (SPOILER) Plus Muska is one of the rare real villains in Miyazaki, a real sadist (he gloats at the death of thousands and threatens to shoot Sheeta's ears off) and he's dealt with appropriately--considering Miyazaki's a filmmaker, to whom eyes are indispensable, that's as cruel a punishment as he possibly can think of.
All this talk of costumes has got me thinking...
The ultimate challenge would be dressing up as an Ohmu, and all fourteen of your eyes can turn red when your date pisses you off. You can charge the buffet table and when you get there, spread spores (a bubblemaker? A portable fog machine?) in the air.
Or a life-sized God Warrior, complete with extendable 'wings,' poisoned halo, and melting limbs. For the party's climax, you can fall apart.
Or as Laputa, complete with (literally) forestlike headgear (bonsai might do nicely). At midnight, the lower half of your costume collapses into rubble.