/* =========================================================================
   ShaftLab — visual identity: "machine drawing on graphite", bronze accent
   (siblings: BeamLab = blue blueprint, FrameLab = teal blueprint)
   ========================================================================= */
:root {
  --bp-bg: #14141b;
  --bp-bg2: #1a1a23;
  --bp-panel: #1e1e28;
  --bp-panel2: #272733;
  --bp-line: #34343f;
  --bp-line2: #474756;
  --bp-ink: #e9e5de;
  --bp-ink-dim: #9c948a;
  --bp-cyan: #e0a458;          /* primary accent: bronze */
  --bp-blue: #5ec8f0;          /* dimensions / secondary */
  --bp-amber: #ffc55c;
  --bp-red: #ff6f6f;
  --bp-green: #6ee7a5;
  --bp-violet: #b197fc;
  --bp-pink: #f472b6;
  --bp-steel: #b8bec9;
  --mono: 'Cascadia Code', 'JetBrains Mono', Consolas, 'Courier New', monospace;
  --sans: 'Segoe UI', system-ui, -apple-system, sans-serif;
  --radius: 10px;
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }

body {
  font-family: var(--sans);
  color: var(--bp-ink);
  background-color: var(--bp-bg);
  background-image:
    linear-gradient(rgba(224, 164, 88, 0.045) 1px, transparent 1px),
    linear-gradient(90deg, rgba(224, 164, 88, 0.045) 1px, transparent 1px),
    linear-gradient(rgba(224, 164, 88, 0.02) 1px, transparent 1px),
    linear-gradient(90deg, rgba(224, 164, 88, 0.02) 1px, transparent 1px);
  background-size: 120px 120px, 120px 120px, 24px 24px, 24px 24px;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* ------------------------------- Header ------------------------------- */
.app-header {
  position: sticky; top: 0; z-index: 50;
  background: rgba(20, 20, 27, 0.93);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--bp-line);
}
.header-inner {
  max-width: 1480px; margin: 0 auto; padding: 0.7rem 1.2rem;
  display: flex; align-items: center; gap: 1.1rem; flex-wrap: wrap;
}
.back-link {
  color: var(--bp-ink-dim); text-decoration: none; font-size: 1.3rem;
  width: 2.1rem; height: 2.1rem; display: grid; place-items: center;
  border: 1px solid var(--bp-line); border-radius: 8px; transition: 0.2s;
}
.back-link:hover { color: var(--bp-cyan); border-color: var(--bp-cyan); }
.brand { display: flex; align-items: center; gap: 0.6rem; }
.brand-mark { width: 50px; height: 27px; color: var(--bp-cyan); }
.brand-text { display: flex; flex-direction: column; line-height: 1.15; }
.brand-name { font-family: var(--mono); font-weight: 700; font-size: 1.25rem; letter-spacing: 0.04em; }
.brand-name::after { content: '_'; color: var(--bp-blue); animation: blink 1.2s steps(1) infinite; }
@keyframes blink { 50% { opacity: 0; } }
.brand-sub { font-size: 0.72rem; color: var(--bp-ink-dim); letter-spacing: 0.08em; text-transform: uppercase; }

.main-tabs { display: flex; gap: 0.4rem; margin-left: auto; }
.main-tab {
  font-family: var(--mono); font-size: 0.92rem; padding: 0.5rem 1.1rem;
  background: transparent; color: var(--bp-ink-dim);
  border: 1px solid var(--bp-line); border-radius: 8px; cursor: pointer; transition: 0.2s;
}
.main-tab:hover { color: var(--bp-ink); border-color: var(--bp-line2); }
.main-tab.active { color: var(--bp-bg); background: var(--bp-cyan); border-color: var(--bp-cyan); font-weight: 600; }
.lang-badge {
  font-family: var(--mono); font-size: 0.78rem; color: var(--bp-ink-dim);
  border: 1px solid var(--bp-line); border-radius: 8px; padding: 0.4rem 0.65rem;
}

/* ------------------------------- Layout ------------------------------- */
main { flex: 1; }
.tab-panel { max-width: 1480px; margin: 0 auto; padding: 1.2rem; }
.calc-layout { display: grid; grid-template-columns: 420px 1fr; gap: 1.2rem; align-items: start; }

.panel {
  background: linear-gradient(180deg, var(--bp-panel), var(--bp-bg2));
  border: 1px solid var(--bp-line);
  border-radius: var(--radius);
  padding: 1rem 1.1rem;
  margin-bottom: 1.2rem;
  position: relative;
}
.panel::before {
  content: ''; position: absolute; inset: 6px; pointer-events: none;
  border: 1px dashed rgba(224, 164, 88, 0.12); border-radius: 6px;
}
.panel-title {
  font-size: 0.95rem; font-weight: 600; letter-spacing: 0.06em; text-transform: uppercase;
  display: flex; align-items: center; gap: 0.55rem; margin-bottom: 0.9rem;
}
.panel-num {
  font-family: var(--mono); font-size: 0.75rem; color: var(--bp-blue);
  border: 1px solid var(--bp-blue); border-radius: 5px; padding: 0.1rem 0.35rem;
}

/* ------------------------------- Forms ------------------------------- */
.field-row {
  display: grid; grid-template-columns: 1fr 165px; gap: 0.6rem;
  align-items: center; margin-bottom: 0.55rem;
}
.field-row label { font-size: 0.85rem; color: var(--bp-ink-dim); }
input[type="number"], select {
  font-family: var(--mono); font-size: 0.88rem;
  background: var(--bp-bg); color: var(--bp-ink);
  border: 1px solid var(--bp-line2); border-radius: 7px;
  padding: 0.4rem 0.5rem; width: 100%;
  transition: border-color 0.2s;
}
input[readonly] { color: var(--bp-cyan); background: rgba(224,164,88,0.06); }
input[type="number"]:focus, select:focus { outline: none; border-color: var(--bp-cyan); }
input[type="number"]::-webkit-inner-spin-button { opacity: 0.4; }
select { cursor: pointer; }
option { background: var(--bp-bg); }

.check-row {
  display: flex; align-items: center; gap: 0.55rem; font-size: 0.83rem;
  color: var(--bp-ink-dim); cursor: pointer; margin-top: 0.55rem;
}
.check-row input { accent-color: var(--bp-cyan); width: 15px; height: 15px; cursor: pointer; }

.hint-line { font-size: 0.75rem; color: var(--bp-ink-dim); line-height: 1.5; margin: 0.55rem 0 0.2rem; }
.hint-line strong { color: var(--bp-cyan); font-weight: 600; }

.load-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.45rem; }
.load-grid.three { grid-template-columns: 1fr 1fr 1fr; }
.load-grid.four { grid-template-columns: 1fr 1fr 1fr 1fr; }
.mini-field label { display: block; font-size: 0.68rem; color: var(--bp-ink-dim); margin-bottom: 0.15rem; font-family: var(--mono); }
.mini-field input, .mini-field select { padding: 0.3rem 0.42rem; font-size: 0.83rem; }

.add-btns { display: flex; gap: 0.4rem; margin-top: 0.3rem; flex-wrap: wrap; }
.btn-add {
  flex: 1; min-width: 78px; display: flex; align-items: center; justify-content: center; gap: 0.35rem;
  font-family: var(--mono); font-size: 0.78rem; padding: 0.45rem 0.3rem;
  background: transparent; color: var(--bp-cyan);
  border: 1px dashed var(--bp-line2); border-radius: 8px; cursor: pointer; transition: 0.2s;
}
.btn-add:hover { border-color: var(--bp-cyan); background: rgba(224, 164, 88, 0.08); }
.btn-add .ico { font-size: 0.95rem; }

/* ------------------------------- Steps ------------------------------- */
.step-card {
  border: 1px solid var(--bp-line); border-left: 3px solid var(--bp-steel);
  border-radius: 8px; padding: 0.55rem 0.65rem; margin-bottom: 0.55rem;
  background: rgba(20, 20, 27, 0.55);
}
.card-head {
  display: flex; align-items: center; gap: 0.5rem; margin-bottom: 0.45rem;
  font-size: 0.82rem; font-weight: 600; letter-spacing: 0.03em;
}
.card-head .ltag { font-family: var(--mono); color: var(--bp-ink-dim); font-weight: 400; font-size: 0.72rem; }
.icon-btn {
  margin-left: auto; background: none; border: 1px solid var(--bp-line); color: var(--bp-ink-dim);
  border-radius: 6px; min-width: 24px; height: 24px; padding: 0 0.35rem;
  cursor: pointer; line-height: 1; transition: 0.2s; font-size: 0.78rem; font-family: var(--mono);
}
.icon-btn:hover { color: var(--bp-cyan); border-color: var(--bp-cyan); }
.icon-btn.danger:hover { color: var(--bp-red); border-color: var(--bp-red); }
.icon-btn + .icon-btn { margin-left: 0.3rem; }

.feat-list { margin-top: 0.5rem; padding-top: 0.45rem; border-top: 1px dashed var(--bp-line); }
.feat-card {
  border: 1px solid var(--bp-line); border-left: 3px solid var(--bp-violet);
  border-radius: 7px; padding: 0.45rem 0.55rem; margin-bottom: 0.4rem;
  background: rgba(177, 151, 252, 0.05);
}
.feat-card .card-head { font-size: 0.76rem; margin-bottom: 0.35rem; }
.feat-add { display: flex; gap: 0.3rem; flex-wrap: wrap; margin-top: 0.35rem; }
.feat-add button {
  font-family: var(--mono); font-size: 0.68rem; padding: 0.22rem 0.45rem;
  background: transparent; color: var(--bp-ink-dim);
  border: 1px dashed var(--bp-line2); border-radius: 6px; cursor: pointer; transition: 0.15s;
}
.feat-add button:hover { color: var(--bp-violet); border-color: var(--bp-violet); }

.geom-summary { font-family: var(--mono); font-size: 0.75rem; color: var(--bp-ink-dim); margin-top: 0.6rem; line-height: 1.65; }
.geom-summary b { color: var(--bp-cyan); font-weight: 600; }

/* ------------------------------- Bearings & loads ------------------------------- */
.sup-card {
  border: 1px solid var(--bp-line); border-left: 3px solid var(--bp-blue);
  border-radius: 8px; padding: 0.55rem 0.65rem; margin-bottom: 0.5rem;
  background: rgba(20, 20, 27, 0.55);
}
.load-card {
  border: 1px solid var(--bp-line); border-left: 3px solid var(--bp-red);
  border-radius: 8px; padding: 0.55rem 0.65rem; margin-bottom: 0.5rem;
  background: rgba(20, 20, 27, 0.55);
}
.load-card.gear { border-left-color: var(--bp-green); }
.load-card.pulley { border-left-color: var(--bp-amber); }
.load-card.torque { border-left-color: var(--bp-cyan); }
.load-note { font-family: var(--mono); font-size: 0.68rem; color: var(--bp-ink-dim); margin-top: 0.35rem; line-height: 1.5; }
.load-note b { color: var(--bp-cyan); font-weight: 600; }

.mat-props, .marin-props {
  font-family: var(--mono); font-size: 0.74rem; color: var(--bp-ink-dim);
  margin: 0.45rem 0 0.6rem; line-height: 1.7;
}
.mat-props b, .marin-props b { color: var(--bp-cyan); font-weight: 600; }
.marin-props { margin-bottom: 0; }

/* ------------------------------- Results ------------------------------- */
.schematic-panel svg { width: 100%; height: auto; display: block; }
#shaftView { background: rgba(20, 20, 27, 0.5); border: 1px solid var(--bp-line); border-radius: 8px; }
.view-tabs { display: flex; gap: 0.35rem; flex-wrap: wrap; margin-bottom: 0.7rem; }
.view-tabs button {
  font-family: var(--mono); font-size: 0.76rem; padding: 0.3rem 0.7rem;
  background: transparent; color: var(--bp-ink-dim);
  border: 1px solid var(--bp-line); border-radius: 7px; cursor: pointer; transition: 0.18s;
}
.view-tabs button:hover { color: var(--bp-ink); border-color: var(--bp-line2); }
.view-tabs button.active { background: var(--bp-panel2); color: var(--bp-cyan); border-color: var(--bp-cyan); font-weight: 600; }

.solve-error, .solve-warn {
  margin-top: 0.6rem; padding: 0.65rem 0.9rem; border-radius: 8px; font-size: 0.86rem; line-height: 1.5;
}
.solve-error { border: 1px solid var(--bp-red); color: var(--bp-red); background: rgba(255, 111, 111, 0.07); }
.solve-warn { border: 1px solid var(--bp-amber); color: var(--bp-amber); background: rgba(255, 197, 92, 0.07); }

.result-cards {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(196px, 1fr));
  gap: 0.8rem; margin-bottom: 1.2rem;
}
.rcard {
  background: linear-gradient(180deg, var(--bp-panel), var(--bp-bg2));
  border: 1px solid var(--bp-line); border-radius: var(--radius); padding: 0.75rem 0.9rem;
}
.rcard .rc-label {
  font-size: 0.67rem; text-transform: uppercase; letter-spacing: 0.09em;
  color: var(--bp-ink-dim); margin-bottom: 0.3rem; display: flex; justify-content: space-between; gap: 0.4rem;
}
.rcard .rc-value { font-family: var(--mono); font-size: 1.25rem; font-weight: 700; }
.rcard .rc-value small { font-size: 0.74rem; color: var(--bp-ink-dim); font-weight: 400; }
.rcard .rc-sub { font-family: var(--mono); font-size: 0.71rem; color: var(--bp-ink-dim); margin-top: 0.2rem; line-height: 1.5; }
.rcard.ok { border-left: 3px solid var(--bp-green); }
.rcard.bad { border-left: 3px solid var(--bp-red); }
.rcard.warn { border-left: 3px solid var(--bp-amber); }
.rcard.neutral { border-left: 3px solid var(--bp-cyan); }

.util-bar { height: 7px; background: var(--bp-bg); border-radius: 4px; margin-top: 0.45rem; overflow: hidden; border: 1px solid var(--bp-line); }
.util-fill { height: 100%; border-radius: 3px; background: var(--bp-green); transition: width 0.3s; }
.util-fill.bad { background: var(--bp-red); }
.util-fill.warn { background: var(--bp-amber); }

.chart-panel { padding-bottom: 0.6rem; }
.chart-head { display: flex; align-items: baseline; justify-content: space-between; margin-bottom: 0.4rem; gap: 0.6rem; }
.chart-head h3 { font-size: 0.88rem; font-weight: 600; letter-spacing: 0.04em; }
.chart-max { font-family: var(--mono); font-size: 0.77rem; color: var(--bp-blue); white-space: nowrap; }
.chart-panel svg { width: 100%; height: 210px; display: block; }
.chart-note { font-size: 0.72rem; color: var(--bp-ink-dim); margin-top: 0.35rem; font-style: italic; line-height: 1.5; }

.res-table { border-collapse: collapse; width: 100%; font-size: 0.78rem; font-family: var(--mono); }
.res-table th, .res-table td { border: 1px solid var(--bp-line); padding: 0.4rem 0.55rem; text-align: left; white-space: nowrap; }
.res-table th { background: var(--bp-panel2); color: var(--bp-cyan); font-weight: 600; }
.res-table td.ok { color: var(--bp-green); }
.res-table td.bad { color: var(--bp-red); }
.res-table td.warn { color: var(--bp-amber); }
.tbl-wrap { overflow-x: auto; }

/* ------------------------------- Textbook ------------------------------- */
.learn-layout { display: grid; grid-template-columns: 300px 1fr; gap: 1.2rem; align-items: start; }
.learn-nav {
  position: sticky; top: 76px;
  background: linear-gradient(180deg, var(--bp-panel), var(--bp-bg2));
  border: 1px solid var(--bp-line); border-radius: var(--radius); padding: 0.7rem; overflow: hidden;
}
.learn-nav button {
  display: flex; align-items: center; gap: 0.6rem; width: 100%; text-align: left;
  background: none; border: none; color: var(--bp-ink-dim); cursor: pointer;
  padding: 0.6rem 0.7rem; border-radius: 8px; font-size: 0.88rem; transition: 0.15s; font-family: var(--sans);
}
.learn-nav button:hover { background: rgba(224, 164, 88, 0.08); color: var(--bp-ink); }
.learn-nav button.active { background: rgba(224, 164, 88, 0.13); color: var(--bp-cyan); font-weight: 600; }
.learn-nav .ch-num { font-family: var(--mono); font-size: 0.7rem; color: var(--bp-blue); min-width: 1.5rem; }

.learn-body {
  background: linear-gradient(180deg, var(--bp-panel), var(--bp-bg2));
  border: 1px solid var(--bp-line); border-radius: var(--radius); padding: 1.6rem 2rem;
  line-height: 1.75; font-size: 0.97rem;
}
.learn-body h2 { font-size: 1.45rem; margin-bottom: 1rem; }
.learn-body h3 { font-size: 1.08rem; margin: 1.5rem 0 0.6rem; color: var(--bp-cyan); }
.learn-body p { margin-bottom: 0.8rem; }
.learn-body ul, .learn-body ol { margin: 0 0 0.9rem 1.4rem; }
.learn-body li { margin-bottom: 0.35rem; }
.learn-body strong { color: var(--bp-amber); font-weight: 600; }
.learn-body em { color: var(--bp-ink-dim); }
.learn-body table { border-collapse: collapse; width: 100%; margin: 0.8rem 0 1.1rem; font-size: 0.86rem; }
.learn-body th, .learn-body td { border: 1px solid var(--bp-line2); padding: 0.45rem 0.6rem; text-align: left; }
.learn-body th { background: var(--bp-panel2); font-weight: 600; color: var(--bp-cyan); }

.formula {
  font-family: var(--mono); text-align: center; margin: 1rem auto; padding: 0.8rem 1rem;
  background: var(--bp-bg); border: 1px solid var(--bp-line2); border-radius: 8px;
  font-size: 1.02rem; overflow-x: auto;
  display: flex; align-items: center; justify-content: center; gap: 0.4rem; flex-wrap: wrap;
}
.fx { font-family: var(--mono); color: var(--bp-cyan); white-space: nowrap; }
.frac { display: inline-flex; flex-direction: column; vertical-align: middle; text-align: center; margin: 0 0.25rem; }
.frac > span { display: block; padding: 0 0.35rem; }
.frac > span:first-child { border-bottom: 1.5px solid currentColor; }
sub, sup { font-size: 0.68em; }

.note-box {
  border-left: 3px solid var(--bp-blue); background: rgba(94, 200, 240, 0.06);
  border-radius: 0 8px 8px 0; padding: 0.7rem 1rem; margin: 0.9rem 0; font-size: 0.9rem;
}
.warn-box {
  border-left: 3px solid var(--bp-red); background: rgba(255, 111, 111, 0.06);
  border-radius: 0 8px 8px 0; padding: 0.7rem 1rem; margin: 0.9rem 0; font-size: 0.9rem;
}
.example-box { border: 1px solid var(--bp-green); border-radius: 8px; padding: 1rem 1.2rem; margin: 1rem 0; }
.example-box .ex-title { font-weight: 700; color: var(--bp-green); margin-bottom: 0.5rem; font-size: 0.92rem; letter-spacing: 0.04em; text-transform: uppercase; }
.try-btn {
  display: inline-block; margin-top: 0.5rem; font-family: var(--mono); font-size: 0.82rem;
  color: var(--bp-bg); background: var(--bp-cyan); border: none; border-radius: 7px;
  padding: 0.45rem 0.9rem; cursor: pointer; transition: 0.2s; font-weight: 600;
}
.try-btn:hover { filter: brightness(1.15); }

.learn-fig { margin: 1rem auto; text-align: center; }
.learn-fig svg { max-width: 100%; height: auto; }
.learn-fig figcaption { font-size: 0.78rem; color: var(--bp-ink-dim); margin-top: 0.3rem; font-style: italic; }

/* ------------------------------- Footer ------------------------------- */
.app-footer {
  border-top: 1px solid var(--bp-line); padding: 1rem 1.2rem; text-align: center;
  font-size: 0.8rem; color: var(--bp-ink-dim);
}
.app-footer a { color: var(--bp-cyan); text-decoration: none; }
.app-footer a:hover { text-decoration: underline; }

/* ------------------------------- Responsive ------------------------------- */
@media (max-width: 1160px) {
  .calc-layout { grid-template-columns: 1fr; }
  .learn-layout { grid-template-columns: 1fr; }
  .learn-nav { position: static; display: flex; flex-wrap: wrap; gap: 0.3rem; }
  .learn-nav button { width: auto; }
}
@media (max-width: 640px) {
  .header-inner { gap: 0.6rem; }
  .brand-sub { display: none; }
  .main-tabs { order: 3; width: 100%; margin-left: 0; }
  .main-tab { flex: 1; }
  .learn-body { padding: 1.1rem 1rem; }
  .load-grid.three, .load-grid.four { grid-template-columns: 1fr 1fr; }
  .field-row { grid-template-columns: 1fr; }
}