/* ── Escape Velocity Simulator ───────────────────────────────────── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg:        #0d1117;
  --surface:   #161b27;
  --surface2:  #1f2535;
  --border:    #2a3050;
  --accent:    #6c7bff;
  --accent-lo: rgba(108,123,255,.22);
  --green:     #3ddc84;
  --red:       #ff5555;
  --gold:      #f5c842;
  --text:      #dde3f0;
  --text-dim:  #6b7a99;
  --font:      'Segoe UI', system-ui, sans-serif;
  --mono:      'Courier New', monospace;
  --radius:    12px;
}

body { background: var(--bg); color: var(--text); font-family: var(--font); min-height: 100vh; padding: 0 16px; }
#app { max-width: 1060px; margin: 0 auto; display: flex; flex-direction: column; gap: 14px; }

/* ── Header ────────────────────────────────────────────────────── */
header { text-align: center; padding: 4px 0; }
header h1 {
  font-size: 1.8rem; font-weight: 700;
  background: linear-gradient(120deg, #6c7bff 0%, #a6b0ff 100%);
  -webkit-background-clip: text; -webkit-text-fill-color: transparent; background-clip: text;
}
.subtitle { color: var(--text-dim); font-size: 0.85rem; margin-top: 3px; }

/* ── Controls bar ──────────────────────────────────────────────── */
.controls-bar {
  display: flex; flex-wrap: wrap; align-items: center; gap: 14px;
  padding: 12px 16px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
}
.ctrl-group { display: flex; align-items: center; gap: 8px; }
.ctrl-label { font-size: 0.72rem; text-transform: uppercase; letter-spacing: .06em; color: var(--text-dim); white-space: nowrap; }

.pill-tabs { display: flex; background: var(--bg); border-radius: 8px; padding: 3px; gap: 2px; }
.pill {
  padding: 5px 13px; border: none; background: transparent; color: var(--text-dim);
  border-radius: 6px; cursor: pointer; font-size: 0.81rem;
  transition: background .18s, color .18s, box-shadow .18s;
}
.pill.active { background: var(--accent); color: #fff; box-shadow: 0 0 12px var(--accent-lo); }
.pill:hover:not(.active) { background: var(--surface2); color: var(--text); }

/* ── Canvas card ───────────────────────────────────────────────── */
.canvas-card {
  width: 100%; background: var(--surface);
  border: 1px solid var(--border); border-radius: var(--radius);
  padding: 8px; position: relative; overflow-x: clip;
}
.canvas-card canvas { display: block; width: 100%; height: auto; cursor: pointer; touch-action: manipulation; }
.canvas-stage { position: relative; }

/* ── Buttons ───────────────────────────────────────────────────── */
.btn {
  padding: 8px 18px; border: none; border-radius: 8px; cursor: pointer;
  font-size: 0.84rem; font-weight: 600; transition: filter .18s, box-shadow .18s, opacity .18s;
}
.btn:disabled { opacity: 0.38; cursor: not-allowed; }
.btn-primary { background: var(--accent); color: #fff; }
.btn-primary:not(:disabled):hover { filter: brightness(1.12); box-shadow: 0 0 12px var(--accent-lo); }
.btn-ghost { background: var(--surface2); color: var(--text); border: 1px solid var(--border); }
.btn-ghost:hover { background: var(--border); }

/* ── Sim controls ─────────────────────────────────────────────── */
.sim-controls {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 14px 18px; display: flex; flex-direction: column; gap: 12px;
}
.sim-row { display: flex; align-items: center; gap: 14px; flex-wrap: wrap; }
.sim-slider-group { display: flex; align-items: center; gap: 10px; flex: 1; min-width: 200px; }
.sim-slider-label { font-size: 0.76rem; font-weight: 700; color: var(--text-dim); white-space: nowrap; min-width: 80px; }
.sim-slider {
  flex: 1; min-width: 0; -webkit-appearance: none; appearance: none; height: 6px;
  background: rgba(255,255,255,.12); border-radius: 3px; outline: none;
  border: 1px solid rgba(255,255,255,.1);
}
.sim-slider::-webkit-slider-runnable-track {
  height: 6px; border-radius: 3px;
  background: linear-gradient(to right, var(--accent-lo), rgba(255,255,255,.12));
}
.sim-slider::-webkit-slider-thumb {
  -webkit-appearance: none; width: 18px; height: 18px; margin-top: -6px;
  border-radius: 50%; background: var(--accent); cursor: pointer;
  box-shadow: 0 0 8px var(--accent-lo); border: 2px solid rgba(255,255,255,.2);
}
.sim-slider::-moz-range-track {
  height: 6px; border-radius: 3px;
  background: linear-gradient(to right, var(--accent-lo), rgba(255,255,255,.12)); border: none;
}
.sim-slider::-moz-range-thumb {
  width: 16px; height: 16px; border: 2px solid rgba(255,255,255,.2);
  border-radius: 50%; background: var(--accent); cursor: pointer;
}

.sim-controls .ctrl-label { min-width: 80px; }
.sim-row .sim-env { flex: 1; min-width: 200px; }
.sim-row .sim-env #body-tabs { margin-left: auto; }

.mass-presets { display: flex; gap: 6px; flex-wrap: wrap; }
.preset-btn {
  padding: 6px 14px; border: 2px solid var(--border); border-radius: 8px;
  background: var(--surface2); color: var(--text-dim); font-size: 0.78rem;
  font-weight: 700; cursor: pointer; transition: border-color .18s, color .18s, background .18s;
}
.preset-btn:hover { border-color: var(--accent); color: var(--text); }
.preset-btn.active { border-color: var(--accent); color: #fff; background: rgba(108,123,255,.18); }

/* ── Speed gauge ──────────────────────────────────────────────── */
.speed-gauge { padding: 4px 2px 10px; }
.sg-track {
  position: relative; height: 12px; border-radius: 6px;
  background: linear-gradient(90deg, #2a3050 0%, #3a3f66 100%);
  border: 1px solid var(--border);
}
.sg-fill {
  position: absolute; left: 0; top: 0; height: 100%; width: 0;
  border-radius: 6px; background: linear-gradient(90deg, #4a5bd8, #6c7bff);
  transition: width .12s linear;
}
.sg-fill.orbit  { background: linear-gradient(90deg, #2e7d55, #3ddc84); }
.sg-fill.escape { background: linear-gradient(90deg, #b58a00, #f5c842); }
.sg-tick {
  position: absolute; top: -4px; height: 20px; width: 2px; background: rgba(255,255,255,.55);
}
.sg-tick span {
  position: absolute; top: -16px; left: 50%; transform: translateX(-50%);
  font-size: 0.6rem; color: var(--text-dim); white-space: nowrap; font-family: var(--mono);
}
.sg-tick-circ { background: var(--green); }
.sg-tick-circ span { color: var(--green); }
.sg-tick-esc  { background: var(--gold); }
.sg-tick-esc span  { color: var(--gold); }
.sg-marker {
  position: absolute; top: 50%; transform: translate(-50%, -50%);
  width: 14px; height: 14px; border-radius: 50%; background: #fff;
  border: 2px solid var(--accent); box-shadow: 0 0 8px rgba(108,123,255,.8);
}

.readout-row {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(130px, 1fr)); gap: 8px;
}
.readout-card {
  background: var(--bg); border: 1px solid var(--border); border-radius: 8px;
  padding: 8px 12px; text-align: center;
}
.outcome-card { border-color: var(--accent); }
.readout-label { font-size: 0.62rem; text-transform: uppercase; letter-spacing: .07em; color: var(--text-dim); margin-bottom: 3px; }
.readout-val { font-family: var(--mono); font-size: 1.15rem; font-weight: 700; color: var(--accent); }
.readout-val.warn { color: var(--red); }
.readout-val.ok { color: var(--green); }
.readout-val.gold { color: var(--gold); }
.readout-unit { font-size: 0.68rem; color: var(--text-dim); margin-left: 2px; }

/* ── Explore mode ──────────────────────────────────────────────── */
.item-selector {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 14px 16px;
}
.is-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(155px, 1fr)); gap: 8px; margin-top: 10px; }
.is-btn {
  padding: 10px 14px; border: 2px solid var(--border); border-radius: 10px;
  background: var(--surface2); color: var(--text-dim); font-size: 0.82rem;
  font-weight: 600; cursor: pointer; text-align: left;
  transition: border-color .18s, color .18s, background .18s, box-shadow .18s;
}
.is-btn:hover { border-color: rgba(108,123,255,.45); color: var(--text); }
.is-btn.active { border-color: var(--accent); color: #fff; background: rgba(108,123,255,.15); box-shadow: 0 0 14px var(--accent-lo); }
.is-btn-name { display: block; font-size: 0.82rem; font-weight: 700; }
.is-btn-sym  { display: block; font-size: 0.68rem; color: var(--accent); margin-top: 2px; font-family: var(--mono); }

.item-info {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px 18px; display: flex; flex-direction: column; gap: 8px;
}
.ii-top { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; }
.ii-name { font-size: 1.15rem; font-weight: 800; color: var(--text); }
.ii-cat-badge {
  font-size: 0.62rem; font-weight: 700; text-transform: uppercase;
  letter-spacing: .07em; padding: 3px 10px; border-radius: 20px;
  background: var(--accent-lo); color: var(--accent);
}
.ii-desc { font-size: 0.85rem; color: var(--text-dim); line-height: 1.65; }

.formula-box {
  background: var(--bg); border: 1px solid var(--border); border-radius: 8px;
  padding: 10px 14px; display: flex; align-items: center; gap: 16px; flex-wrap: wrap;
}
.fb-formula { font-family: var(--mono); font-size: 1.1rem; font-weight: 700; color: var(--accent); }
.fb-unit { font-size: 0.78rem; color: var(--text-dim); }

.example-box {
  background: var(--surface2); border: 1px solid var(--border); border-radius: 8px;
  padding: 12px 14px;
}
.example-box h4 { font-size: 0.72rem; text-transform: uppercase; letter-spacing: .08em; color: var(--accent); margin-bottom: 8px; }
.example-box .ex-problem { font-size: 0.84rem; color: var(--text); margin-bottom: 8px; line-height: 1.6; }
.example-box .ex-step { font-size: 0.8rem; color: var(--text-dim); line-height: 1.6; padding: 2px 0; }
.example-box .ex-step strong { color: var(--green); font-family: var(--mono); }

/* ── Practice mode ─────────────────────────────────────────────── */
.practice-panel {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px 18px;
}
.pp-prompt { font-size: 0.92rem; font-weight: 600; color: var(--text); margin-bottom: 14px; line-height: 1.6; }
.pp-input-row { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.pp-input {
  flex: 1; min-width: 120px; max-width: 220px;
  padding: 10px 14px; border: 2px solid var(--border); border-radius: 8px;
  background: var(--bg); color: var(--text); font-family: var(--mono);
  font-size: 1rem; font-weight: 700; transition: border-color .18s;
}
.pp-input:focus { outline: none; border-color: var(--accent); }
.pp-unit { font-size: 0.88rem; color: var(--text-dim); font-weight: 600; }
.pp-bottom { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; margin-top: 14px; }
.feedback { font-size: 0.88rem; font-weight: 600; }
.feedback.ok  { color: var(--green); }
.feedback.err { color: var(--red); }

.solution-panel {
  background: var(--surface2); border: 1px solid var(--border); border-radius: 8px;
  padding: 14px 16px; margin-top: 12px;
}
.solution-panel h4 { font-size: 0.72rem; text-transform: uppercase; letter-spacing: .08em; color: var(--accent); margin-bottom: 8px; }
.sol-step { font-size: 0.82rem; color: var(--text-dim); line-height: 1.7; padding: 2px 0; }
.sol-step strong { color: var(--green); font-family: var(--mono); }

.practice-bar {
  display: flex; align-items: center; gap: 12px; flex-wrap: wrap;
  padding: 12px 16px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
}
.pbar-score { font-size: 0.84rem; color: var(--text-dim); margin-left: auto; white-space: nowrap; }
.pbar-score span { color: var(--text); font-weight: 700; }

/* ── Quiz panels ───────────────────────────────────────────────── */
.question-panel {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px 18px;
}
.qp-prompt { font-size: 0.88rem; font-weight: 600; color: var(--text); margin-bottom: 12px; line-height: 1.6; }
.answer-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 10px; }
.answer-btn {
  padding: 14px 16px; border: 2px solid var(--border); border-radius: 10px;
  background: var(--surface2); color: var(--text); font-size: 0.88rem;
  font-weight: 600; cursor: pointer; text-align: center;
  transition: border-color .18s, background .18s, color .18s, transform .12s;
}
.answer-btn:hover:not(.locked) { border-color: var(--accent); background: rgba(108,123,255,.06); }
.answer-btn.correct { border-color: var(--green); background: rgba(61,220,132,.12); color: var(--green); }
.answer-btn.wrong { border-color: var(--red); background: rgba(255,85,85,.08); color: var(--red); }
.answer-btn.locked { cursor: default; opacity: 0.6; }
.answer-btn.correct.locked { opacity: 1; }

.quiz-bar {
  display: flex; align-items: center; gap: 12px; flex-wrap: wrap;
  padding: 12px 16px;
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
}
.qbar-counter { display: flex; align-items: baseline; gap: 3px; background: var(--bg); border: 1px solid var(--border); border-radius: 8px; padding: 4px 12px; }
.qbar-q-label { font-size: 0.7rem; font-weight: 700; color: var(--accent); text-transform: uppercase; letter-spacing: .08em; }
.qbar-q-num { font-family: var(--mono); font-size: 1.3rem; font-weight: 700; color: var(--text); line-height: 1; }
.qbar-q-sep { font-size: 0.82rem; color: var(--text-dim); }
.qbar-q-total { font-family: var(--mono); font-size: 0.88rem; color: var(--text-dim); }

.quiz-result {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 20px 22px; display: flex; flex-direction: column; gap: 14px;
}
.qr-header { display: flex; align-items: flex-start; justify-content: space-between; }
.qr-title-wrap { display: flex; flex-direction: column; gap: 5px; }
.qr-title  { font-size: 1.1rem; font-weight: 700; color: var(--text); }
.qr-stars  { font-size: 1.2rem; letter-spacing: 3px; }
.qr-score-wrap { text-align: right; }
.qr-score { font-family: var(--mono); font-size: 2.2rem; font-weight: 700; line-height: 1; text-shadow: 0 0 14px currentColor; }
.qr-score.perfect { color: var(--gold); }
.qr-score.good { color: var(--green); }
.qr-score.poor { color: var(--red); }
.qr-verdict { font-size: 0.72rem; color: var(--text-dim); margin-top: 3px; }
.qr-rows { display: flex; flex-direction: column; gap: 7px; }
.qr-row {
  display: grid; grid-template-columns: 30px 1fr 26px; align-items: center; gap: 10px;
  background: var(--surface2); border: 1px solid var(--border); border-left-width: 3px;
  border-radius: 8px; padding: 9px 12px;
}
.qr-row.ok  { border-left-color: var(--green); }
.qr-row.err { border-left-color: var(--red); }
.qr-qnum { font-size: 0.72rem; font-weight: 700; color: var(--accent); }
.qr-detail { font-size: 0.78rem; color: var(--text-dim); }
.qr-detail strong { color: var(--text); }
.qr-mark { text-align: right; font-size: 1rem; font-weight: 700; }
.qr-row.ok .qr-mark { color: var(--green); }
.qr-row.err .qr-mark { color: var(--red); }

.quiz-input-row { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; margin-bottom: 10px; }
.qi-input {
  flex: 1; min-width: 120px; max-width: 200px;
  padding: 10px 14px; border: 2px solid var(--border); border-radius: 8px;
  background: var(--bg); color: var(--text); font-family: var(--mono);
  font-size: 1rem; font-weight: 700; transition: border-color .18s;
}
.qi-input:focus { outline: none; border-color: var(--accent); }
.qi-unit { font-size: 0.84rem; color: var(--text-dim); font-weight: 600; }

#body-tabs .pill { min-width: 52px; text-align: center; }

/* ── Responsive ────────────────────────────────────────────────── */
@media (max-width: 768px) {
  .answer-grid { grid-template-columns: 1fr 1fr; }
  .is-grid { grid-template-columns: repeat(auto-fill, minmax(130px, 1fr)); }
  .controls-bar { gap: 10px; }
  .readout-row { grid-template-columns: repeat(2, 1fr); }
  .sim-slider-group { min-width: 160px; }
}
@media (max-width: 500px) {
  header h1 { font-size: 1.4rem; }
  .subtitle  { font-size: 0.78rem; }
  .controls-bar { padding: 10px 12px; gap: 8px; }
  .pill { padding: 5px 10px; font-size: 0.76rem; }
  .answer-grid { grid-template-columns: 1fr; }
  .is-grid { grid-template-columns: 1fr 1fr; }
  .readout-row { grid-template-columns: 1fr 1fr; }
  .sim-slider-group { min-width: 100%; flex-wrap: wrap; }
  .sim-slider { flex: 1 1 120px; }
  .sim-slider-group .stepper { margin-left: 90px; }
  .preset-btn { padding: 5px 10px; font-size: 0.72rem; }
}

@media (pointer: coarse) {
  .step-btn { width: 40px; height: 40px; }
  .pill { min-height: 40px; }
  .ct-btn, .ct-toggle, .preset-btn { min-height: 44px; }
}

/* ═══ Stepper inputs ═════════════════════════════════════════════ */
.stepper {
  display: inline-flex; align-items: center; gap: 4px;
  background: var(--bg); border: 1px solid var(--border); border-radius: 8px; padding: 2px;
}
.step-btn {
  width: 26px; height: 26px; padding: 0;
  border: none; background: var(--surface2); color: var(--text);
  border-radius: 6px; cursor: pointer; font-size: 0.95rem; font-weight: 700;
  line-height: 1; display: inline-flex; align-items: center; justify-content: center;
  transition: background 0.15s, color 0.15s;
}
.step-btn:hover { background: var(--accent); color: #fff; }
.step-btn:focus-visible { outline: 2px solid var(--accent); outline-offset: 1px; }
.step-input {
  width: 56px; padding: 4px 6px;
  border: none; background: transparent; color: var(--accent);
  font-family: var(--mono); font-size: 0.88rem; font-weight: 700; text-align: center;
}
.step-input::-webkit-outer-spin-button,
.step-input::-webkit-inner-spin-button { -webkit-appearance: none; margin: 0; }
.step-input { -moz-appearance: textfield; }
.step-input:focus { outline: none; }
.step-unit { font-size: 0.74rem; color: var(--text-dim); padding-right: 6px; min-width: 28px; }

/* ═══ Canvas display-controls ════════════════════════════════════ */
.canvas-toggles {
  position: absolute; top: 8px; left: 8px; z-index: 4;
  background: rgba(13,17,30,0.82);
  -webkit-backdrop-filter: blur(3px); backdrop-filter: blur(3px);
  border: 1px solid rgba(139,157,195,0.22); border-radius: 9px;
  box-shadow: 0 4px 14px rgba(0,0,0,0.32);
}
.canvas-toggles > summary {
  list-style: none; cursor: pointer; user-select: none;
  display: flex; align-items: center; gap: 7px;
  padding: 6px 10px; white-space: nowrap;
  font-size: 0.66rem; font-weight: 700; text-transform: uppercase; letter-spacing: 0.05em;
  color: var(--text); border-radius: 9px; transition: background 0.12s, color 0.12s;
}
.canvas-toggles > summary::-webkit-details-marker { display: none; }
.canvas-toggles > summary::marker { content: ''; }
.canvas-toggles > summary:hover { background: rgba(108,123,255,0.10); color: var(--accent); }
.canvas-toggles .cvt-ico { flex-shrink: 0; color: var(--accent); }
.canvas-toggles .cvt-caret { margin-left: auto; padding-left: 4px; color: var(--text-dim); font-size: 0.7rem; transition: transform 0.2s; }
.canvas-toggles[open] > summary .cvt-caret { transform: rotate(180deg); color: var(--accent); }
.canvas-toggles[open] > summary { border-bottom: 1px solid rgba(139,157,195,0.18); border-radius: 9px 9px 0 0; }
.canvas-toggles .cvt-body { display: flex; flex-direction: column; gap: 5px; padding: 8px 11px 9px; }
.canvas-toggles .cvt-item {
  display: flex; align-items: center; gap: 6px;
  font-size: 0.72rem; color: var(--text-dim); cursor: pointer; white-space: nowrap; transition: color 0.12s;
}
.canvas-toggles .cvt-item:hover { color: var(--text); }
.canvas-toggles .cvt-item input[type="checkbox"] {
  accent-color: var(--accent); width: 14px; height: 14px; cursor: pointer; flex-shrink: 0;
}

/* ═══ Body planet — animated rotating icon ═══════════════════════ */
.gravity-planet {
  position: absolute; top: 10px; right: 10px; z-index: 4;
  width: 46px; height: 46px; border-radius: 50%;
  overflow: hidden; isolation: isolate;
  border: 1px solid rgba(255,255,255,0.10);
  box-shadow: inset -7px -6px 13px rgba(0,0,0,0.55), 0 2px 10px rgba(0,0,0,0.45);
}
.gravity-planet .gp-surface {
  position: absolute; top: -10%; left: 0; width: 200%; height: 120%;
  background-repeat: repeat-x; background-size: 50% 100%;
  animation: gp-spin 7s linear infinite;
}
@keyframes gp-spin { from { transform: translateX(0); } to { transform: translateX(-50%); } }
.gravity-planet::after {
  content: ''; position: absolute; inset: 0; border-radius: 50%; z-index: 1; pointer-events: none;
  background:
    radial-gradient(circle at 30% 28%, rgba(255,255,255,0.45), rgba(255,255,255,0) 42%),
    radial-gradient(circle at 72% 76%, rgba(0,0,0,0.5), rgba(0,0,0,0) 60%);
}
.gp-earth .gp-surface {
  background-color: #1f5fa6;
  background-image:
    radial-gradient(ellipse 26% 34% at 18% 38%, #3fa055 0 70%, transparent 73%),
    radial-gradient(ellipse 20% 26% at 55% 66%, #45a85a 0 70%, transparent 73%),
    radial-gradient(ellipse 15% 20% at 82% 30%, #2f8a46 0 70%, transparent 73%),
    radial-gradient(ellipse 18% 14% at 40% 14%, rgba(255,255,255,0.25) 0 70%, transparent 73%);
}
.gp-moon .gp-surface {
  background-color: #a6abb3;
  background-image:
    radial-gradient(ellipse 14% 14% at 22% 36%, #7d828b 0 62%, transparent 66%),
    radial-gradient(ellipse 9% 9% at 60% 62%, #82878f 0 62%, transparent 66%),
    radial-gradient(ellipse 7% 7% at 80% 28%, #767b84 0 62%, transparent 66%),
    radial-gradient(ellipse 5% 5% at 42% 78%, #888d95 0 62%, transparent 66%);
}
.gp-mars .gp-surface {
  background-color: #c1542d;
  background-image:
    radial-gradient(ellipse 30% 22% at 25% 60%, #9e3f1f 0 70%, transparent 73%),
    radial-gradient(ellipse 20% 16% at 65% 38%, #a8472a 0 70%, transparent 73%),
    radial-gradient(ellipse 16% 14% at 86% 70%, #8f3a20 0 70%, transparent 73%),
    radial-gradient(ellipse 42% 12% at 50% 5%, #e8e3d8 0 70%, transparent 74%);
}
.gravity-planet.gp-notice { animation: gp-pop 0.9s ease-out; }
@keyframes gp-pop {
  0%   { transform: scale(1);    box-shadow: 0 0 0 0 rgba(108,123,255,0.75), inset -7px -6px 13px rgba(0,0,0,0.55), 0 2px 10px rgba(0,0,0,0.45); }
  30%  { transform: scale(1.18); }
  100% { transform: scale(1);    box-shadow: 0 0 0 13px rgba(108,123,255,0),    inset -7px -6px 13px rgba(0,0,0,0.55), 0 2px 10px rgba(0,0,0,0.45); }
}
@media (prefers-reduced-motion: reduce) {
  .gravity-planet .gp-surface { animation: none; }
  .gravity-planet.gp-notice { animation: none; }
}

/* ═══ Escape-velocity badge beside the planet icon ═══════════════ */
.gp-vesc {
  position: absolute; top: 46px; right: 62px; z-index: 4;
  display: flex; align-items: center; gap: 6px; white-space: nowrap;
  background: rgba(13,17,30,0.82);
  -webkit-backdrop-filter: blur(3px); backdrop-filter: blur(3px);
  border: 1px solid rgba(108,123,255,0.35); border-radius: 8px;
  padding: 4px 9px; box-shadow: 0 4px 14px rgba(0,0,0,0.32);
  pointer-events: none;
}
.gp-vesc-lbl { font-size: 0.62rem; font-weight: 700; color: var(--text-dim); }
.gp-vesc-lbl sub { font-size: 0.72em; }
.gp-vesc-val { font-family: var(--mono); font-size: 0.82rem; font-weight: 700; color: var(--accent); }
.gp-vesc-val #gp-vesc-val { color: var(--accent); }
@media (max-width: 500px) {
  .gp-vesc { top: 40px; right: 50px; padding: 3px 7px; gap: 4px; }
  .gp-vesc-val { font-size: 0.72rem; }
  .gp-vesc-lbl { font-size: 0.56rem; }
}

/* ═══ Disabled drag toggle (Moon has no atmosphere) ══════════════ */
.canvas-toolbar .ct-toggle.disabled { opacity: 0.42; cursor: not-allowed; }
.canvas-toolbar .ct-toggle.disabled:hover {
  border-color: rgba(139,157,195,0.22); color: var(--text-dim); background: var(--surface2);
}
.canvas-toolbar .ct-toggle.disabled input[type="checkbox"] { cursor: not-allowed; }

/* ═══ CSS motion-path rocket overlay ═════════════════════════════ */
/* Driven by CSS `offset-path` so it animates on the compositor and keeps
   moving even when JS timers / rAF are throttled by a hidden/embedded view. */
.ev-rocket {
  position: absolute; left: 0; top: 0; z-index: 5;
  width: 24px; height: 24px; display: none; pointer-events: none;
  offset-anchor: 50% 50%; offset-rotate: auto;
  filter: drop-shadow(0 0 5px rgba(108,123,255,0.85));
}
.ev-rocket svg { overflow: visible; display: block; }
@keyframes ev-fly { from { offset-distance: 0%; } to { offset-distance: 100%; } }
@media (prefers-reduced-motion: reduce) {
  .ev-rocket { animation-duration: 0.001s !important; }
}

/* ═══ Canvas hint banner ═════════════════════════════════════════ */
.canvas-hint {
  position: absolute; bottom: 14px; left: 50%; transform: translateX(-50%);
  background: rgba(245,200,66,0.95); color: #1a1a2e;
  padding: 6px 30px 6px 12px; border-radius: 20px;
  font-size: 0.78rem; font-weight: 600; box-shadow: 0 4px 12px rgba(0,0,0,0.35);
  z-index: 4; max-width: calc(100% - 40px);
}
.canvas-hint.hidden { display: none; }
.hint-close {
  position: absolute; right: 6px; top: 50%; transform: translateY(-50%);
  width: 20px; height: 20px; padding: 0;
  border: none; background: transparent; color: #1a1a2e;
  font-size: 1.1rem; line-height: 1; cursor: pointer; font-weight: 700;
}

/* ═══ Canvas toolbar ═════════════════════════════════════════════ */
.canvas-toolbar {
  display: flex; flex-wrap: nowrap; gap: 4px;
  margin-top: 8px; padding: 8px 6px;
  background: linear-gradient(180deg, rgba(30,38,66,0.35), rgba(20,26,46,0.25));
  border: 1px solid rgba(139,157,195,0.22);
  border-radius: 9px; box-shadow: inset 0 1px 0 rgba(255,255,255,0.03);
}
.canvas-toolbar .ct-btn {
  flex: 1 1 0;
  display: inline-flex; align-items: center; justify-content: center; gap: 5px;
  appearance: none; background: var(--surface2);
  border: 1px solid rgba(139,157,195,0.22);
  border-radius: 6px; color: var(--text);
  padding: 8px 8px; font-size: 0.75rem; font-weight: 600;
  letter-spacing: 0.02em; white-space: nowrap; min-width: 0; cursor: pointer;
  transition: background 0.12s ease, color 0.12s ease, border-color 0.12s ease, transform 0.1s ease;
}
.canvas-toolbar .ct-btn .ct-icon  { font-size: 0.9rem; line-height: 1; }
.canvas-toolbar .ct-btn .ct-label { overflow: hidden; text-overflow: ellipsis; }
.canvas-toolbar .ct-btn:hover:not(:disabled) {
  background: var(--accent-lo); border-color: rgba(108,123,255,0.55);
  color: var(--accent); transform: translateY(-1px);
}
.canvas-toolbar .ct-btn:active:not(:disabled) { transform: translateY(0); }
.canvas-toolbar .ct-btn:disabled { opacity: 0.40; cursor: not-allowed; background: var(--surface); color: var(--text-dim); }
.canvas-toolbar .ct-btn:focus-visible { outline: 2px solid var(--gold); outline-offset: -1px; }

.canvas-toolbar .ct-toggle {
  flex: 1 1 0;
  display: inline-flex; align-items: center; justify-content: center; gap: 6px;
  background: var(--surface2);
  border: 1px solid rgba(139,157,195,0.22);
  border-radius: 6px; color: var(--text-dim);
  padding: 8px 8px; font-size: 0.75rem; font-weight: 600;
  white-space: nowrap; min-width: 0; cursor: pointer;
  transition: background 0.12s, color 0.12s, border-color 0.12s;
}
.canvas-toolbar .ct-toggle input[type="checkbox"] {
  accent-color: var(--accent); width: 15px; height: 15px; cursor: pointer; flex-shrink: 0;
}
.canvas-toolbar .ct-toggle:hover { border-color: rgba(108,123,255,0.45); color: var(--text); }
.canvas-toolbar .ct-toggle.checked { color: var(--accent); border-color: rgba(108,123,255,0.55); background: var(--accent-lo); }
.canvas-toolbar .ct-toggle .ct-label { overflow: hidden; text-overflow: ellipsis; }

.canvas-toolbar .ct-btn-calc { flex-grow: 1.7; }
.canvas-toolbar .ct-toggle  { flex-grow: 2.2; }
.canvas-toolbar .ct-btn-calc {
  background: linear-gradient(180deg, rgba(245,200,66,0.20), rgba(245,200,66,0.06));
  border-color: rgba(245,200,66,0.45); color: var(--gold); font-weight: 700;
}
.canvas-toolbar .ct-btn-calc:hover:not(:disabled) {
  background: linear-gradient(180deg, rgba(245,200,66,0.34), rgba(245,200,66,0.14));
  border-color: var(--gold); color: var(--gold);
}
.canvas-toolbar .ct-btn-fire {
  background: linear-gradient(180deg, #6c7bff, #4a5bd8);
  border-color: rgba(255,255,255,0.15); color: #fff; font-weight: 700;
}
.canvas-toolbar .ct-btn-fire:hover:not(:disabled) {
  filter: brightness(1.1); background: linear-gradient(180deg, #7d8bff, #5566e0);
  border-color: var(--accent); color: #fff;
}

/* ═══ Calculation modal ══════════════════════════════════════════ */
.calc-modal {
  display: none; position: fixed; inset: 0; z-index: 1200;
  background: rgba(0,0,0,0.72); backdrop-filter: blur(4px);
  align-items: flex-start; justify-content: center;
  padding: 24px 16px; overflow-y: auto;
}
.calc-modal.active { display: flex; }
.calc-modal-box {
  background: var(--surface); border: 1px solid rgba(139,157,195,0.25); border-radius: 12px;
  width: 100%; max-width: 760px;
  display: flex; flex-direction: column;
  box-shadow: 0 24px 64px rgba(0,0,0,0.6);
  max-height: calc(100vh - 48px); overflow: hidden;
}
.calc-modal-header {
  display: flex; align-items: center; justify-content: space-between;
  padding: 14px 20px; border-bottom: 1px solid var(--border);
  background: var(--surface2); flex-shrink: 0;
}
.calc-modal-title { font-size: 1rem; font-weight: 800; color: var(--text); }
.calc-modal-close {
  width: 34px; height: 34px;
  border: 1px solid var(--border); border-radius: 8px;
  background: var(--bg); color: var(--text-dim);
  font-size: 1.4rem; line-height: 1; padding: 0;
  display: flex; align-items: center; justify-content: center; cursor: pointer;
  transition: border-color 0.15s, color 0.15s, background 0.15s;
}
.calc-modal-close:hover { border-color: var(--accent); color: var(--text); background: var(--surface2); }
.calc-modal-body { padding: 16px 20px; overflow-y: auto; display: flex; flex-direction: column; gap: 12px; }

.cs-inputs {
  background: rgba(108,123,255,0.08);
  border: 1px solid rgba(108,123,255,0.25); border-radius: 8px;
  padding: 12px 14px; display: flex; flex-direction: column; gap: 8px;
}
.cs-badge {
  display: inline-block; padding: 3px 12px; border-radius: 20px;
  background: rgba(108,123,255,0.22); color: var(--accent);
  font-size: 0.72rem; font-weight: 700;
  text-transform: uppercase; letter-spacing: 0.06em; align-self: flex-start;
}
.cs-given { display: flex; flex-wrap: wrap; gap: 6px 16px; }
.cs-given span { font-family: var(--mono); font-size: 0.82rem; color: var(--text); }
.cs-si-note { font-size: 0.72rem; color: var(--text-dim); margin: 0; }

.cs-step {
  background: var(--bg); border: 1px solid var(--border); border-radius: 8px;
  padding: 12px 14px; display: flex; flex-direction: column; gap: 6px;
}
.cs-step-hd { display: flex; align-items: baseline; gap: 8px; flex-wrap: wrap; }
.cs-num {
  font-size: 0.64rem; font-weight: 800;
  text-transform: uppercase; letter-spacing: 0.06em;
  color: var(--accent); background: rgba(108,123,255,0.18);
  padding: 2px 8px; border-radius: 20px; white-space: nowrap;
}
.cs-title { font-size: 0.9rem; font-weight: 700; color: var(--text); }
.cs-formula {
  font-size: 0.95rem; color: var(--text);
  background: var(--surface2); border-radius: 6px;
  padding: 8px 12px; border-left: 3px solid var(--accent);
}
.cs-calc   { font-family: var(--mono); font-size: 0.8rem; color: var(--text); white-space: pre-wrap; line-height: 1.7; }
.cs-result { font-size: 0.88rem; color: var(--text-dim); margin-top: 2px; }
.cs-result strong { font-family: var(--mono); font-size: 0.95rem; color: var(--green); }

/* ═══ Learning panels ════════════════════════════════════════════ */
.learn-panels {
  margin-top: 4px; padding: 14px;
  background: linear-gradient(180deg, rgba(30,38,66,0.6), rgba(20,26,46,0.6));
  border: 1px solid rgba(139,157,195,0.2); border-radius: 12px;
}
.learn-head {
  display: flex; align-items: center; justify-content: space-between;
  gap: 12px; flex-wrap: wrap;
  padding-bottom: 10px; border-bottom: 1px solid rgba(139,157,195,0.18); margin-bottom: 12px;
}
.learn-head-title { font-size: 0.95rem; font-weight: 700; color: var(--text); letter-spacing: 0.01em; }
.learn-head-actions { display: flex; gap: 8px; }
.learn-toggle-all {
  padding: 5px 12px;
  background: rgba(108,123,255,0.12); border: 1px solid rgba(108,123,255,0.35);
  color: var(--accent); border-radius: 6px;
  font-size: 0.78rem; font-weight: 600; cursor: pointer; transition: background 0.15s, color 0.15s;
}
.learn-toggle-all:hover { background: rgba(108,123,255,0.25); color: var(--text); }
.learn-toggle-all:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

.learn-card {
  border: 1px solid rgba(139,157,195,0.18); border-radius: 10px;
  background: rgba(13,17,30,0.55); margin-bottom: 10px; overflow: hidden; transition: border-color 0.2s;
}
.learn-card:last-child { margin-bottom: 0; }
.learn-card[open] { border-color: rgba(108,123,255,0.35); }
.learn-card > summary {
  list-style: none; cursor: pointer; padding: 10px 14px;
  display: flex; align-items: center; gap: 10px; flex-wrap: wrap;
  font-size: 0.88rem; font-weight: 700; color: var(--text);
  user-select: none; transition: background 0.15s; position: relative;
}
.learn-card > summary::-webkit-details-marker { display: none; }
.learn-card > summary::marker { display: none; content: ''; }
.learn-card > summary:hover { background: rgba(108,123,255,0.08); }
.learn-card > summary::after {
  content: '\25BE'; margin-left: auto; color: var(--text-dim); font-size: 0.78rem; transition: transform 0.2s;
}
.learn-card[open] > summary::after { transform: rotate(180deg); color: var(--accent); }

.lp-badge {
  display: inline-flex; align-items: center; justify-content: center;
  width: 22px; height: 22px; border-radius: 6px;
  background: rgba(108,123,255,0.18); font-size: 0.9rem; flex-shrink: 0; color: var(--accent);
}
.lp-sub { color: var(--text-dim); font-weight: 500; font-size: 0.78rem; }
.learn-body { padding: 12px 14px 14px; }
.learn-body .eq-line { padding: 6px 0; border-bottom: 1px dashed rgba(139,157,195,0.15); overflow-x: auto; }
.learn-body .eq-line:last-child { border-bottom: none; }
.learn-body .eq-label { font-size: 0.74rem; color: var(--text-dim); margin-bottom: 4px; }
.learn-body .coach-tip {
  padding: 8px 12px; margin: 6px 0;
  background: rgba(108,123,255,0.08); border-left: 3px solid var(--accent);
  border-radius: 6px; font-size: 0.82rem; color: var(--text); line-height: 1.55;
}
.learn-body .coach-tip strong { color: var(--accent); }
.energy-bars { display: flex; flex-direction: column; gap: 8px; }
.energy-bar-row { display: flex; align-items: center; gap: 10px; }
.energy-bar-label { font-size: 0.74rem; color: var(--text-dim); min-width: 110px; }
.energy-bar-track { flex: 1; height: 14px; background: var(--surface2); border-radius: 7px; overflow: hidden; border: 1px solid var(--border); }
.energy-bar-fill { height: 100%; border-radius: 7px; }
.energy-bar-val { font-family: var(--mono); font-size: 0.76rem; color: var(--text); min-width: 90px; text-align: right; }

/* ═══ Context menu ═══════════════════════════════════════════════ */
.ctx-menu {
  display: none; position: fixed; z-index: 1100;
  background: var(--surface); border: 1px solid var(--border); border-radius: 8px;
  box-shadow: 0 12px 32px rgba(0,0,0,0.6); padding: 4px; min-width: 180px;
}
.ctx-menu.active { display: flex; flex-direction: column; }
.ctx-item {
  padding: 8px 12px; border: none; background: transparent;
  color: var(--text); text-align: left; font-size: 0.84rem; cursor: pointer; border-radius: 6px;
}
.ctx-item:hover { background: var(--surface2); color: var(--accent); }

/* ═══ SEO article figures / screenshots ═════════════════════════ */
.seo-figure { margin: 22px auto; text-align: center; max-width: 780px; }
.seo-figure img {
  width: 100%; height: auto; display: block; margin: 0 auto;
  border-radius: 10px; border: 1px solid var(--border);
  box-shadow: 0 8px 26px rgba(0,0,0,0.4);
}
.seo-figcap { font-size: 0.82rem; color: var(--text-dim); margin-top: 9px; line-height: 1.55; }
.seo-figcap strong { color: var(--accent); }
.seo-figrow {
  display: grid; grid-template-columns: 1fr 1fr; gap: 16px; margin: 22px 0;
}
.seo-figrow figure { margin: 0; }
.seo-figrow img {
  width: 100%; height: auto; display: block;
  border-radius: 10px; border: 1px solid var(--border);
  box-shadow: 0 6px 20px rgba(0,0,0,0.38);
}
.seo-figrow figcaption { font-size: 0.78rem; color: var(--text-dim); margin-top: 7px; line-height: 1.5; text-align: center; }
.seo-figrow figcaption strong { color: var(--accent); }
@media (max-width: 600px) { .seo-figrow { grid-template-columns: 1fr; } }

/* ═══ Featured snippet table ═════════════════════════════════════ */
.snippet-table {
  width: 100%; border-collapse: collapse; margin: 14px 0;
  background: var(--surface); border: 1px solid var(--border); border-radius: 8px; overflow: hidden;
}
.snippet-table th, .snippet-table td {
  padding: 8px 12px; text-align: left; font-size: 0.84rem; border-bottom: 1px solid var(--border);
}
.snippet-table th {
  background: var(--surface2); color: var(--accent);
  font-weight: 700; text-transform: uppercase; letter-spacing: 0.04em; font-size: 0.74rem;
}
.snippet-table td:nth-child(2) { font-family: var(--mono); color: var(--text); }
.snippet-table tbody tr:last-child td { border-bottom: none; }
.snippet-table tbody tr:hover { background: rgba(108,123,255,0.05); }

@media (max-width: 540px) {
  .canvas-toolbar { flex-wrap: wrap; }
  .canvas-toolbar .ct-btn,
  .canvas-toolbar .ct-toggle { flex: 1 1 28%; font-size: 0.72rem; padding: 8px 6px; min-height: 40px; }
}
@media (max-width: 500px) {
  .stepper .step-input { width: 44px; font-size: 0.82rem; }
  .step-btn { width: 24px; height: 24px; }
  .step-unit { font-size: 0.7rem; min-width: 22px; padding-right: 4px; }
  .canvas-toggles > summary { padding: 5px 8px; font-size: 0.6rem; gap: 5px; }
  .canvas-toggles .cvt-body { padding: 6px 9px 7px; gap: 4px; }
  .canvas-toggles .cvt-item { font-size: 0.64rem; gap: 5px; }
  .canvas-toggles .cvt-item input[type="checkbox"] { width: 12px; height: 12px; }
  .canvas-hint { display: none; }
  .gravity-planet { width: 38px; height: 38px; top: 8px; right: 8px; }
  .calc-modal { padding: 12px 8px; }
  .calc-modal-box { max-height: calc(100vh - 24px); }
  .calc-modal-body { padding: 12px 12px; }
  .cs-step { padding: 10px; }
  .learn-panels { padding: 10px; }
  .learn-card > summary { padding: 10px 12px; font-size: 0.82rem; }
  .lp-sub { display: none; }
  .learn-body { padding: 10px 12px 12px; }
  .learn-head-title { font-size: 0.85rem; }
  .learn-toggle-all { padding: 4px 10px; font-size: 0.72rem; }
  .snippet-table th, .snippet-table td { padding: 6px 8px; font-size: 0.76rem; }
  .energy-bar-label { min-width: 80px; font-size: 0.68rem; }
  .energy-bar-val { min-width: 66px; font-size: 0.68rem; }
}

/* INTERLINK-START  header quick-links */
.head-actions{display:flex;align-items:center;gap:8px;margin-left:auto;flex-wrap:wrap;justify-content:flex-end;}
.btn-link{display:inline-flex;align-items:center;gap:7px;padding:5px 12px;border-radius:8px;font-size:.82rem;font-weight:700;text-decoration:none;cursor:pointer;background:var(--surface2,#1f2535);color:var(--text,#dde3f0);border:1.5px solid var(--border,#2a3050);white-space:nowrap;transition:border-color .18s,background .18s,color .18s;}
.btn-link:hover{border-color:var(--accent,#6c7bff);background:var(--accent-lo,rgba(108,123,255,.18));color:#fff;}
.btn-link img{width:20px;height:20px;border-radius:4px;flex:none;}
.btn-link .lbl{line-height:1;}
@media(max-width:560px){.btn-link .lbl{display:none;}.btn-link{padding:5px 9px;}}
/* INTERLINK-END */