Devlog #5: real mode, smaller black holes, and the 4500-body incident

this update started with a dangerous sentence:

“can we make it as real as possible?”

which is always how you end up rewriting half the rules of your tiny gravity sandbox.

the big new thing is realism mode. sandbox mode is still the weird toybox: fixed black holes, white holes, dramatic nonsense, maximum chaos. real mode is stricter. white holes get removed, black holes are no longer pinned in place, and compact objects actually move under gravity like everything else. black holes are still terrifying, but now they can drift, get tugged around, and become part of the system instead of being an immovable stage prop.

i also split visual size from collision size.

before, a black hole’s visible radius and collision radius were basically the same idea. that made them feel too chunky. now bodies have a visual radius and a collision radius. stars and planets can still look big and readable, but black holes can have a smaller actual eating zone while keeping the dramatic accretion disk visuals. neutron stars stay tiny and dense, which feels much better.

then came high-speed realism collisions.

in real mode, fast planet/star impacts can now fragment instead of just merging. the impact throws out visual debris and a few physical asteroid chunks, so collisions feel more like violent breakup events instead of every crash becoming one bigger blob.

and then i discovered a very funny problem.

the launched fragments counted as bodies. those bodies immediately collided with each other. then those collisions made more bodies. then those bodies collided too. a small-ish crash could casually become 4500 bodies and turn the browser into soup.

so that got fixed.

impact debris is now mostly visual particles, with only a small capped number of real chunks. asteroid fragments also cannot recursively fragment again, which means you still get the cool spray of debris without accidentally inventing an infinite universe generator.

the sim now has a clearer split:

• sandbox mode is for cosmic nonsense
• real mode is for cleaner physical behavior
• visual particles are for spectacle
• real bodies are for things that should actually affect gravity

that last distinction matters a lot. not every glowing speck deserves to be in the Barnes-Hut tree, emotionally or computationally.

the best moments now are these messy almost-real disasters: a star explodes, leaves a neutron star, nearby bodies get torn up, a black hole drifts through the debris, and the whole thing looks like some cursed astronomy textbook diagram that learned how to party.

next i probably want capture tools: hide UI, follow-cam, maybe a screenshot-friendly slow motion key. because the sim is now very good at making moments that disappear right before i can take a picture.

thanks for reading :)