Initial project setup: Rust/WASM solar system simulator with SvelteKit frontend

- Rust workspace with 4 crates: orbital-mechanics, mass-driver-core, mass-driver-wasm, mass-driver-backend
- Keplerian orbital mechanics engine with JPL elements for 14 bodies (Sun, 8 planets, Pluto, Ceres, Europa, Titan, Ganymede)
- Kepler equation solver and orbital position computation compiled to WASM
- SvelteKit frontend with Tailwind CSS, Canvas2D renderer showing animated solar system
- Orbit ellipses, planet dots with labels, Sun glow, grid, scale bar, pan/zoom controls
- Time controls (play/pause, 5 speed levels, date picker) driving live simulation
- 2D/3D view toggle (3D placeholder for Threlte integration)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/mass-driver-wasm/src/api.rs

@@ -0,0 +1,59 @@
+use orbital_mechanics::bodies;
+use orbital_mechanics::orbits;
+use wasm_bindgen::prelude::*;
+
+/// Initialize the WASM module. Called once on page load.
+#[wasm_bindgen]
+pub fn init() -> Result<(), JsValue> {
+    web_sys::console::log_1(&"mass-driver WASM initialized".into());
+    Ok(())
+}
+
+/// Get the number of celestial bodies in the simulation.
+#[wasm_bindgen]
+pub fn get_body_count() -> usize {
+    bodies::all_bodies().len()
+}
+
+/// Get positions of all celestial bodies at a given Julian Date.
+///
+/// Returns a Float64Array of [x0, y0, z0, x1, y1, z1, ...] in AU.
+#[wasm_bindgen]
+pub fn get_body_positions_at_epoch(jd: f64) -> Vec<f64> {
+    let all = bodies::all_bodies();
+    orbits::all_positions_at_epoch(&all, jd)
+}
+
+/// Get body names as a JSON array of strings.
+#[wasm_bindgen]
+pub fn get_body_names() -> String {
+    let all = bodies::all_bodies();
+    let names: Vec<&str> = all.iter().map(|b| b.name).collect();
+    serde_json::to_string(&names).unwrap()
+}
+
+/// Get body colors as a flat array [r0, g0, b0, r1, g1, b1, ...].
+#[wasm_bindgen]
+pub fn get_body_colors() -> Vec<u8> {
+    let all = bodies::all_bodies();
+    all.iter().flat_map(|b| b.color.iter().copied()).collect()
+}
+
+/// Get body radii in km as a Float64Array.
+#[wasm_bindgen]
+pub fn get_body_radii() -> Vec<f64> {
+    let all = bodies::all_bodies();
+    all.iter().map(|b| b.radius_km).collect()
+}
+
+/// Get orbit points for a given body, sampled around its full orbit.
+/// Returns a Float64Array of [x0, y0, z0, x1, y1, z1, ...] in AU.
+/// `samples` is the number of points around the orbit.
+#[wasm_bindgen]
+pub fn get_orbit_points(body_id: usize, jd: f64, samples: usize) -> Vec<f64> {
+    let all = bodies::all_bodies();
+    if body_id >= all.len() || body_id == bodies::id::SUN {
+        return vec![];
+    }
+    orbits::orbit_points(&all, body_id, jd, samples)
+}