// Solar System mode (Wave 4) — "Travel to…". Leaves the Earth OSINT globe and
// renders a heliocentric orrery: the Sun + 8 planets as spheres textured with
// real (CC BY 4.0, self-hosted) imagery, at their TRUE current positions
// (Schlyter series), with orbits. Click a destination to fly there.
//
// Cesium's globe is Earth-at-origin, so the mode HIDES the globe + all Earth
// layers and places the Sun at the scene origin; exiting restores everything.
export default function initSolarSystem(ctx) {
const { viewer, Cesium, lib } = ctx;
const scene = viewer.scene;
// ---- astronomy (Schlyter low-precision, heliocentric ecliptic AU) ----
const D2R = Math.PI / 180;
const rev = (x) => x - Math.floor(x / 360) * 360;
const ELEM = {
Mercury: (d) => ({ N: 48.3313 + 3.24587e-5 * d, i: 7.0047 + 5.00e-8 * d, w: 29.1241 + 1.01444e-5 * d, a: 0.387098, e: 0.205635 + 5.59e-10 * d, M: 168.6562 + 4.0923344368 * d }),
Venus: (d) => ({ N: 76.6799 + 2.46590e-5 * d, i: 3.3946 + 2.75e-8 * d, w: 54.8910 + 1.38374e-5 * d, a: 0.723330, e: 0.006773 - 1.302e-9 * d, M: 48.0052 + 1.6021302244 * d }),
Mars: (d) => ({ N: 49.5574 + 2.11081e-5 * d, i: 1.8497 - 1.78e-8 * d, w: 286.5016 + 2.92961e-5 * d, a: 1.523688, e: 0.093405 + 2.516e-9 * d, M: 18.6021 + 0.5240207766 * d }),
Jupiter: (d) => ({ N: 100.4542 + 2.76854e-5 * d, i: 1.3030 - 1.557e-7 * d, w: 273.8777 + 1.64505e-5 * d, a: 5.20256, e: 0.048498 + 4.469e-9 * d, M: 19.8950 + 0.0830853001 * d }),
Saturn: (d) => ({ N: 113.6634 + 2.38980e-5 * d, i: 2.4886 - 1.081e-7 * d, w: 339.3939 + 2.97661e-5 * d, a: 9.55475, e: 0.055546 - 9.499e-9 * d, M: 316.9670 + 0.0334442282 * d }),
Uranus: (d) => ({ N: 74.0005 + 1.3978e-5 * d, i: 0.7733 + 1.9e-8 * d, w: 96.6612 + 3.0565e-5 * d, a: 19.18171 - 1.55e-8 * d, e: 0.047318 + 7.45e-9 * d, M: 142.5905 + 0.011725806 * d }),
Neptune: (d) => ({ N: 131.7806 + 3.0173e-5 * d, i: 1.7700 - 2.55e-7 * d, w: 272.8461 - 6.027e-6 * d, a: 30.05826 + 3.313e-8 * d, e: 0.008606 + 2.15e-9 * d, M: 260.2471 + 0.005995147 * d }),
};
const dayNumber = (t) => Cesium.JulianDate.toDate(t).getTime() / 86400000 - 10956.0;
function helio(name, d) {
const el = ELEM[name](d);
const N = el.N * D2R, i = el.i * D2R, w = el.w * D2R, e = el.e, M = rev(el.M) * D2R;
let E = M + e * Math.sin(M) * (1 + e * Math.cos(M));
for (let k = 0; k < 6; k++) E = E - (E - e * Math.sin(E) - M) / (1 - e * Math.cos(E));
const xv = el.a * (Math.cos(E) - e), yv = el.a * Math.sqrt(1 - e * e) * Math.sin(E);
const v = Math.atan2(yv, xv), r = Math.hypot(xv, yv), u = v + w;
return {
x: r * (Math.cos(N) * Math.cos(u) - Math.sin(N) * Math.sin(u) * Math.cos(i)),
y: r * (Math.sin(N) * Math.cos(u) + Math.cos(N) * Math.sin(u) * Math.cos(i)),
z: r * Math.sin(u) * Math.sin(i),
};
}
function earthHelio(d) {
const w = 282.9404 + 4.70935e-5 * d, e = 0.016709 - 1.151e-9 * d, M = rev(356.0470 + 0.9856002585 * d) * D2R;
let E = M + e * Math.sin(M) * (1 + e * Math.cos(M));
const xv = Math.cos(E) - e, yv = Math.sqrt(1 - e * e) * Math.sin(E);
const v = Math.atan2(yv, xv), r = Math.hypot(xv, yv), lon = v + w * D2R;
return { x: -r * Math.cos(lon), y: -r * Math.sin(lon), z: 0 }; // Earth = −(Sun geocentric)
}
// ---- scaling (tuned for a readable orrery, not true scale) ----
const AU_UNIT = 4.0e7; // ~Earth orbit display radius
const distScale = (au) => AU_UNIT * Math.pow(au, 0.72); // gentle outer compression
const BODY_UNIT = 3.4e6; // exaggerated so bodies read at orrery scale
const bodyRadius = (km, isSun) => isSun ? 1.6e7 : BODY_UNIT * Math.pow(km / 6371, 0.4);
function scaledPos(vec) { // ecliptic AU {x,y,z} → scene Cartesian3
const au = Math.hypot(vec.x, vec.y, vec.z) || 1e-6;
const s = distScale(au) / au;
return new Cesium.Cartesian3(vec.x * s, vec.y * s, vec.z * s);
}
// Real 3D spheres textured with self-hosted CC BY 4.0 / NASA imagery. `obliq` =
// axial tilt in degrees (Venus ~177° reads upside-down; Uranus ~98° lies on its
// side) — applied as a constant orientation so each planet leans correctly.
const BODIES = [
{ key: 'sun', name: '☉ Sun', tex: 'textures/2k_sun.jpg', km: 696000, sun: true, color: '#ffcf6b' },
{ key: 'mercury', name: '☿ Mercury', tex: 'textures/hd_mercury.jpg', km: 2439.7, color: '#9a8d80', obliq: 0.03 },
{ key: 'venus', name: '♀ Venus', tex: 'textures/hd_venus.jpg', km: 6051.8, color: '#d8b56a', obliq: 177.4 },
{ key: 'earth', name: '🜨 Earth', tex: 'textures/hd_earth.jpg', km: 6371, color: '#5b8fd0', obliq: 23.44 },
{ key: 'mars', name: '♂ Mars', tex: 'textures/hd_mars.jpg', km: 3389.5, color: '#c1502a', obliq: 25.19 },
{ key: 'jupiter', name: '♃ Jupiter', tex: 'textures/hd_jupiter.jpg', km: 69911, color: '#d9c9a3', obliq: 3.13 },
{ key: 'saturn', name: '♄ Saturn', tex: 'textures/hd_saturn.jpg', km: 58232, color: '#e6dbb0', obliq: 26.73, ring: 'textures/hd_saturn_ring.png' },
{ key: 'uranus', name: '⛢ Uranus', tex: 'textures/hd_uranus.jpg', km: 25362, color: '#9fdce4', obliq: 97.77 },
{ key: 'neptune', name: '♆ Neptune', tex: 'textures/2k_neptune.jpg', km: 24622, color: '#456fe0', obliq: 28.32 },
];
const ds = new Cesium.CustomDataSource('solarsystem');
ds.show = false;
viewer.dataSources.add(ds);
const bodyEntities = {}; // key → entity (for travel-to framing)
function posOf(key, d) {
if (key === 'sun') return new Cesium.Cartesian3(0, 0, 0);
if (key === 'earth') return scaledPos(earthHelio(d));
return scaledPos(helio(key.charAt(0).toUpperCase() + key.slice(1), d));
}
// Orthographic planet disc from an equirectangular texture, drawn onto a canvas
// used as a BILLBOARD image. Billboards render instantly (no async worker
// geometry), always face the camera, and are unlit — reliable where a 3D
// ellipsoid + hidden globe is not. Still reads as a real 3D planet.
const discCache = {};
function makeDisc(b) {
if (discCache[b.key]) return discCache[b.key];
const S = 256, R = S / 2, cv = document.createElement('canvas'); cv.width = cv.height = S;
const g = cv.getContext('2d');
discCache[b.key] = cv; // return now; fill in once the texture loads
const img = new Image();
img.onload = () => {
const iw = img.width, ih = img.height, src = document.createElement('canvas');
src.width = iw; src.height = ih; const sg = src.getContext('2d'); sg.drawImage(img, 0, 0);
const sd = sg.getImageData(0, 0, iw, ih).data;
const out = g.createImageData(S, S), od = out.data;
const lx = -0.5, ly = 0.55, lz = 0.67; // light from upper-left-front
for (let y = 0; y < S; y++) for (let x = 0; x < S; x++) {
const nx = (x - R) / R, ny = (R - y) / R, r2 = nx * nx + ny * ny, oi = (y * S + x) * 4;
if (r2 > 1) { od[oi + 3] = 0; continue; }
const nz = Math.sqrt(1 - r2);
const lat = Math.asin(ny), lon = Math.atan2(nx, nz);
let u = lon / (2 * Math.PI) + 0.5; u -= Math.floor(u);
const vv = 0.5 - lat / Math.PI;
const si = (Math.min(ih - 1, (vv * ih) | 0) * iw + Math.min(iw - 1, (u * iw) | 0)) * 4;
const shade = b.sun ? 1 : Math.max(0.14, nx * lx + ny * ly + nz * lz) * 0.85 + 0.15;
od[oi] = sd[si] * shade; od[oi + 1] = sd[si + 1] * shade; od[oi + 2] = sd[si + 2] * shade; od[oi + 3] = 255;
}
g.putImageData(out, 0, 0);
// The billboard uploaded a blank canvas at creation time; re-assign the now
// -drawn canvas so Cesium re-uploads the real planet image to the atlas.
if (bodyEntities[b.key]) bodyEntities[b.key].billboard.image = cv;
};
img.src = b.tex;
return cv;
}
// Constant axial tilt about +X (Saturn's matches its ring plane; Uranus rolls on
// its side at 98°). NOTE: the orientation MUST be constant — a time-varying
// orientation pushes the ellipsoid onto Cesium's dynamic-geometry path, which
// only supports solid-colour materials and renders the planet blank white. A
// static orientation keeps the image material; you still orbit planets by hand.
const X_AXIS = new Cesium.Cartesian3(1, 0, 0);
function tiltQuat(b) {
return Cesium.Quaternion.fromAxisAngle(X_AXIS, (b.obliq || 0) * D2R);
}
// Saturn's ring-plane normal = its tilted pole (so ring ⟂ pole, aligned to sphere).
function ringNormal(obliqDeg) {
const t = obliqDeg * D2R;
return new Cesium.Cartesian3(0, -Math.sin(t), Math.cos(t));
}
function build(d) {
ds.entities.removeAll();
for (const b of BODIES) {
const pos = posOf(b.key, d);
const r = bodyRadius(b.km, b.sun);
// The Sun is a star: keep it a bright, always-lit billboard disc (a lit
// ellipsoid would show a dark hemisphere). Planets are real 3D spheres.
if (b.sun) {
const ent = ds.entities.add({
name: b.name,
position: pos,
billboard: {
image: makeDisc(b),
scaleByDistance: new Cesium.NearFarScalar(r * 2.5, 2.4, 9e8, 0.12),
disableDepthTestDistance: Number.POSITIVE_INFINITY,
},
label: labelGraphics(b),
});
bodyEntities[b.key] = ent;
continue;
}
const ent = ds.entities.add({
name: b.name,
position: pos,
orientation: tiltQuat(b),
ellipsoid: {
radii: new Cesium.Cartesian3(r, r, r),
material: new Cesium.ImageMaterialProperty({ image: b.tex, color: Cesium.Color.WHITE }),
slicePartitions: 64, stackPartitions: 64,
// Only render the real sphere once you're close enough for it to read as a
// textured planet. Far away it minifies to a grey ball — hide it and show
// the colored dot instead. Clean handoff at r*30.
distanceDisplayCondition: new Cesium.DistanceDisplayCondition(0.0, r * 30),
},
// Colored dot + label are the orrery-overview representation; they vanish as
// you approach (r*30) and the textured 3D planet takes over.
point: {
pixelSize: 7,
color: Cesium.Color.fromCssColorString(b.color),
outlineColor: Cesium.Color.fromCssColorString('#05080b'), outlineWidth: 1,
distanceDisplayCondition: new Cesium.DistanceDisplayCondition(r * 30, 9e9),
disableDepthTestDistance: Number.POSITIVE_INFINITY,
},
label: labelGraphics(b),
});
bodyEntities[b.key] = ent;
// Saturn's rings: a flat quad in the equatorial plane, textured with a
// top-down ring annulus (transparent centre + corners). Depth-tested so the
// planet occludes the far half of the ring — the real Saturn silhouette.
if (b.ring) {
const side = r * 6.6; // hole ≈ planet radius, outer edge ≈ 3.1 radii
ds.entities.add({
position: pos,
plane: {
plane: new Cesium.Plane(ringNormal(b.obliq), 0.0),
dimensions: new Cesium.Cartesian2(side, side),
material: new Cesium.ImageMaterialProperty({ image: b.ring, transparent: true }),
// Match the sphere's visibility window (r*30). Beyond it the ring both
// minifies to an ugly opaque grey card AND would float without a planet,
// so hide it — at that range Saturn is just its labelled dot.
distanceDisplayCondition: new Cesium.DistanceDisplayCondition(0.0, r * 30),
},
});
}
// Orbit: trace one full revolution by sweeping the anomaly.
// arcType NONE = straight segments in space (not draped on an ellipsoid).
const pts = [];
for (let a = 0; a <= 360; a += 3) {
const v = b.key === 'earth' ? earthHelioAt(d, a) : helioAt(b.key, d, a);
pts.push(scaledPos(v));
}
ds.entities.add({
polyline: { positions: pts, width: 1.5, arcType: Cesium.ArcType.NONE, material: lib.cz('#6a86c0', 0.6) },
});
}
}
function labelGraphics(b) {
return {
text: b.name, font: '13px "Segoe UI", system-ui, sans-serif',
fillColor: Cesium.Color.WHITE, outlineColor: Cesium.Color.fromCssColorString('#05080b'),
outlineWidth: 3, style: Cesium.LabelStyle.FILL_AND_OUTLINE,
verticalOrigin: Cesium.VerticalOrigin.TOP, pixelOffset: new Cesium.Cartesian2(0, 12),
disableDepthTestDistance: Number.POSITIVE_INFINITY,
};
}
// Orbit sampling: recompute a body's heliocentric position at mean-anomaly `deg`.
function helioAt(key, d, deg) {
const name = key.charAt(0).toUpperCase() + key.slice(1);
const el = ELEM[name](d);
const N = el.N * D2R, i = el.i * D2R, w = el.w * D2R, e = el.e, M = deg * D2R;
let E = M + e * Math.sin(M) * (1 + e * Math.cos(M));
for (let k = 0; k < 6; k++) E = E - (E - e * Math.sin(E) - M) / (1 - e * Math.cos(E));
const xv = el.a * (Math.cos(E) - e), yv = el.a * Math.sqrt(1 - e * e) * Math.sin(E);
const v = Math.atan2(yv, xv), r = Math.hypot(xv, yv), u = v + w;
return { x: r * (Math.cos(N) * Math.cos(u) - Math.sin(N) * Math.sin(u) * Math.cos(i)), y: r * (Math.sin(N) * Math.cos(u) + Math.cos(N) * Math.sin(u) * Math.cos(i)), z: r * Math.sin(u) * Math.sin(i) };
}
function earthHelioAt(d, deg) {
const w = 282.9404 + 4.70935e-5 * d, e = 0.016709 - 1.151e-9 * d, M = deg * D2R;
let E = M + e * Math.sin(M) * (1 + e * Math.cos(M));
const xv = Math.cos(E) - e, yv = Math.sqrt(1 - e * e) * Math.sin(E);
const v = Math.atan2(yv, xv), r = Math.hypot(xv, yv), lon = v + w * D2R;
return { x: -r * Math.cos(lon), y: -r * Math.sin(lon), z: 0 };
}
// ---- mode enter / exit ----
let active = false;
const saved = { dataSources: [], primitives: [], globe: true, atmo: true, sky: true, animate: true, light: null, far: 5e8, near: 0.1, collide: true };
// Cesium's animated camera.flyTo does NOT progress in this mode (its flight tween
// sits idle out here 1e8 m off Earth with the globe hidden) — but setView works
// perfectly. So drive our own eased per-frame tween: lerp position + orientation
// and setView each frame. Guaranteed smooth because setView is reliable.
let flightTick = null;
const V3 = Cesium.Cartesian3;
function flyCamera(destPos, destDir, destUp, duration) {
if (flightTick) { flightTick(); flightTick = null; }
const cam = scene.camera;
const startPos = cam.positionWC.clone();
const startDir = cam.directionWC.clone();
const startUp = cam.upWC.clone();
const t0 = performance.now();
flightTick = scene.preRender.addEventListener(() => {
let u = (performance.now() - t0) / 1000 / duration;
if (u > 1) u = 1;
const e = u * u * (3 - 2 * u); // smoothstep ease in/out
const pos = V3.lerp(startPos, destPos, e, new V3());
let dir = V3.normalize(V3.lerp(startDir, destDir, e, new V3()), new V3());
let up = V3.normalize(V3.lerp(startUp, destUp, e, new V3()), new V3());
const right = V3.normalize(V3.cross(dir, up, new V3()), new V3());
up = V3.normalize(V3.cross(right, dir, new V3()), new V3()); // re-orthonormalize
scene.camera.setView({ destination: pos, orientation: { direction: dir, up } });
if (u >= 1 && flightTick) { flightTick(); flightTick = null; }
});
}
function enter() {
if (active) return;
active = true;
const d = dayNumber(viewer.clock.currentTime);
build(d);
// Hide every Earth layer: entity data sources + billboard primitives.
saved.dataSources = [];
for (let i = 0; i < viewer.dataSources.length; i++) {
const s = viewer.dataSources.get(i);
if (s === ds) continue;
saved.dataSources.push([s, s.show]); s.show = false;
}
// NOTE: do NOT blanket-hide scene.primitives by duck-typing — that also hides
// Cesium's shared DataSourceDisplay collections (the very ones our planets
// render into). The bespoke billboard layers (aircraft/military/adsb/radius)
// sit at Earth-surface coords → a tiny speck near the Sun in the orrery, so
// leaving them visible is harmless.
saved.primitives = [];
saved.globe = scene.globe.show; scene.globe.show = false;
saved.atmo = scene.globe.showGroundAtmosphere; scene.globe.showGroundAtmosphere = false;
saved.sky = scene.skyAtmosphere.show; scene.skyAtmosphere.show = false;
saved.animate = viewer.clock.shouldAnimate; viewer.clock.shouldAnimate = false; // freeze the snapshot
// The scene spans ~1e9 m — well past Cesium's default 5e8 far plane, which
// would clip every body. Widen it (and drop the surface-collision limit so
// you can fly far out); restored on exit.
saved.far = scene.camera.frustum.far; scene.camera.frustum.far = 6e9;
// Push the near plane out too: with a 6e9 far plane, a 0.1 near destroys depth
// precision and the starfield/scene stop drawing. 1e5 is fine at orrery scale.
saved.near = scene.camera.frustum.near; scene.camera.frustum.near = 1e5;
saved.collide = scene.screenSpaceCameraController.enableCollisionDetection;
scene.screenSpaceCameraController.enableCollisionDetection = false;
scene.screenSpaceCameraController.maximumZoomDistance = 6e9;
// Portrait key-light: source sits upper-left-front of the camera, so the lit
// hemisphere of whatever you orbit stays upper-left — every 3D sphere reads
// with a graceful terminator from any angle, and (since it tracks the camera)
// there's no "sun is over there but lit from here" contradiction.
saved.light = scene.light;
// Intensity is deliberately low: the equirect maps are near-albedo-1 in
// places, so anything above ~0.5 clamps the lit hemisphere to pure white
// (no HDR). 0.42 keeps the texture + Saturn's rings rich and readable.
scene.light = new Cesium.DirectionalLight({ direction: scene.camera.directionWC.clone(), intensity: 0.42 });
const _ld = new Cesium.Cartesian3();
headlight = scene.preRender.addEventListener((s) => {
const c = s.camera;
Cesium.Cartesian3.multiplyByScalar(c.rightWC, 0.5, _ld);
Cesium.Cartesian3.add(_ld, Cesium.Cartesian3.multiplyByScalar(c.upWC, -0.55, new Cesium.Cartesian3()), _ld);
Cesium.Cartesian3.add(_ld, Cesium.Cartesian3.multiplyByScalar(c.directionWC, 0.67, new Cesium.Cartesian3()), _ld);
Cesium.Cartesian3.normalize(_ld, scene.light.direction);
});
ds.show = true;
document.getElementById('hud').style.display = 'none';
panel.style.display = 'block';
document.getElementById('ss-btn').classList.add('active');
// Swoop out from "Sun in your face" (camera starts at the old Earth-surface
// spot, and the Sun now sits where Earth's centre was) to a clean oblique view
// of the whole system.
flyCamera(
new Cesium.Cartesian3(1.6e8, -3.4e8, 2.6e8),
Cesium.Cartesian3.normalize(new Cesium.Cartesian3(-1.6e8, 3.4e8, -2.6e8), new Cesium.Cartesian3()),
new Cesium.Cartesian3(0, 0, 1),
2.6,
);
}
let headlight = null;
function exit() {
if (!active) return;
active = false;
if (flightTick) { flightTick(); flightTick = null; } // stop any in-progress swoop
ds.show = false;
for (const [s, show] of saved.dataSources) s.show = show;
for (const [p, show] of saved.primitives) p.show = show;
scene.globe.show = saved.globe;
scene.globe.showGroundAtmosphere = saved.atmo;
scene.skyAtmosphere.show = saved.sky;
viewer.clock.shouldAnimate = saved.animate;
if (headlight) { headlight(); headlight = null; }
if (saved.light) scene.light = saved.light;
scene.camera.frustum.far = saved.far;
if (saved.near != null) scene.camera.frustum.near = saved.near;
scene.screenSpaceCameraController.enableCollisionDetection = saved.collide;
scene.screenSpaceCameraController.maximumZoomDistance = Infinity;
document.getElementById('hud').style.display = '';
panel.style.display = 'none';
document.getElementById('ss-btn').classList.remove('active');
// Instant, reliable return to the OSINT globe (animated flyTo is dead in this
// mode; setView always works). Nadir view over the configured home spot.
scene.camera.setView({
destination: Cesium.Cartesian3.fromDegrees(ctx.CONFIG.camera.lon, ctx.CONFIG.camera.lat, ctx.CONFIG.camera.height),
orientation: { heading: 0, pitch: -Math.PI / 2, roll: 0 },
});
}
function travelTo(key) {
const b = BODIES.find((x) => x.key === key);
if (!b) return;
if (key === 'earth') { // Earth = home; drop back to the OSINT globe
exit();
return;
}
// Deterministic framing in WORLD space. flyTo(entity)/flyToBoundingSphere both
// misbehave out here (the ENU frame they offset within is degenerate 2e8 m off
// Earth), so compute the destination + orientation directly. Camera sits up and
// to the side of the ecliptic → a 3/4 view that shows Saturn's ring tilt.
const ent = bodyEntities[key];
const pos = ent.position.getValue(viewer.clock.currentTime);
const r = bodyRadius(b.km, b.sun);
const range = (b.sun ? 3.0 : b.ring ? 6.0 : 5.0) * r;
const V = Cesium.Cartesian3;
const offDir = V.normalize(new V(0.55, -0.25, 0.45), new V());
const dest = V.add(pos, V.multiplyByScalar(offDir, range, new V()), new V());
const dir = V.negate(offDir, new V());
const right = V.normalize(V.cross(dir, new V(0, 0, 1), new V()), new V());
const up = V.normalize(V.cross(right, dir, new V()), new V());
flyCamera(dest, dir, up, 2.2);
}
// ---- UI: enter button + destination panel ----
const btn = document.createElement('button');
btn.id = 'ss-btn';
btn.type = 'button';
btn.textContent = '◉ Solar System';
btn.title = 'Leave Earth and travel the solar system';
btn.addEventListener('click', () => (active ? exit() : enter()));
document.body.appendChild(btn);
const panel = document.createElement('aside');
panel.id = 'ss-panel';
panel.style.display = 'none';
panel.innerHTML = `TRAVEL TO
`;
const dests = panel.querySelector('.ss-dests');
for (const b of BODIES) {
const d = document.createElement('button');
d.className = 'ss-dest';
d.textContent = b.name;
d.addEventListener('click', () => travelTo(b.key));
dests.appendChild(d);
}
const back = document.createElement('button');
back.className = 'ss-dest ss-back';
back.textContent = '↩ Return to Earth (OSINT)';
back.addEventListener('click', exit);
panel.appendChild(back);
document.body.appendChild(panel);
return { enter, exit, isActive: () => active };
}