/* ===== Engineering Calculator Hub — design tokens ===== */
:root {
  --bg: #0d1117;
  --bg-panel: #141b24;
  --bg-panel-2: #1a2230;
  --bg-inset: #0a0f16;
  --line: #263241;
  --line-soft: #1d2733;
  --text: #e7edf3;
  --text-dim: #93a3b5;
  --text-faint: #5b6b7d;
  --amber: #e8a33d;
  --amber-dim: #8a6428;
  --cyan: #35d0c0;
  --green: #3fb950;
  --red: #f0666a;
  --blue: #5b9dd9;
  --font-display: 'Barlow Condensed', 'Inter', sans-serif;
  --font-body: 'Inter', system-ui, sans-serif;
  --font-mono: 'JetBrains Mono', 'SFMono-Regular', Menlo, monospace;
  --radius: 6px;
  --shadow: 0 8px 24px rgba(0,0,0,0.35);
}
[data-theme="light"] {
  --bg: #eef1f4;
  --bg-panel: #ffffff;
  --bg-panel-2: #f4f6f8;
  --bg-inset: #e6eaee;
  --line: #d7dee5;
  --line-soft: #e3e8ed;
  --text: #17222e;
  --text-dim: #4c5c6c;
  --text-faint: #8393a3;
  --amber-dim: #f0d19c;
  --shadow: 0 8px 24px rgba(20,30,40,0.08);
}

* { box-sizing: border-box; }
html, body { height: 100%; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-body);
  font-size: 14.5px;
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}
body::before {
  /* faint blueprint grid, signature texture */
  content: "";
  position: fixed; inset: 0; pointer-events: none; z-index: 0;
  background-image:
    linear-gradient(var(--line-soft) 1px, transparent 1px),
    linear-gradient(90deg, var(--line-soft) 1px, transparent 1px);
  background-size: 32px 32px;
  opacity: 0.35;
}
h1, h2, h3, h4 { font-family: var(--font-display); font-weight: 600; letter-spacing: 0.01em; margin: 0 0 .4em; }
h1 { font-size: 2rem; }
h2 { font-size: 1.5rem; }
h3 { font-size: 1.15rem; text-transform: uppercase; letter-spacing: 0.06em; color: var(--text-dim); font-size: .8rem; }
a { color: inherit; }
button, input, select { font-family: inherit; font-size: inherit; color: inherit; }

/* ===== App shell ===== */
#app { display: flex; min-height: 100vh; position: relative; z-index: 1; }

.sidebar {
  width: 240px; flex-shrink: 0;
  background: var(--bg-panel);
  border-right: 1px solid var(--line);
  display: flex; flex-direction: column;
  position: sticky; top: 0; height: 100vh;
}
.brand {
  padding: 18px 18px 14px;
  border-bottom: 1px solid var(--line);
  display: flex; align-items: center; gap: 10px;
}
.brand-mark {
  width: 38px; height: 38px; border-radius: 50%;
  object-fit: cover; flex-shrink: 0; background: #fff;
  box-shadow: 0 0 0 1px var(--line);
}
.brand-text { font-family: var(--font-display); font-weight: 700; font-size: 1.05rem; line-height: 1.1; }
.brand-text small { display: block; font-family: var(--font-mono); font-size: .62rem; color: var(--text-faint); letter-spacing: .08em; text-transform: uppercase; margin-top: 2px; }

.nav { flex: 1; overflow-y: auto; padding: 10px 8px; }
.nav-group { margin-bottom: 4px; }
.nav-label { font-size: .68rem; text-transform: uppercase; letter-spacing: .08em; color: var(--text-faint); padding: 12px 10px 4px; }
.nav-item {
  display: flex; align-items: center; gap: 10px;
  padding: 8px 10px; border-radius: var(--radius); cursor: pointer;
  color: var(--text-dim); text-decoration: none; font-size: .88rem;
  border-left: 2px solid transparent;
}
.nav-item:hover { background: var(--bg-panel-2); color: var(--text); }
.nav-item.active { background: var(--bg-panel-2); color: var(--amber); border-left-color: var(--amber); }
.nav-item .ic { width: 16px; text-align: center; font-family: var(--font-mono); font-size: .8rem; opacity: .8;}

.sidebar-foot { padding: 10px; border-top: 1px solid var(--line); display: flex; gap: 8px; }
.theme-toggle, .icon-btn {
  flex: 1; padding: 8px; border-radius: var(--radius); border: 1px solid var(--line);
  background: var(--bg-panel-2); cursor: pointer; font-size: .78rem; color: var(--text-dim);
}
.theme-toggle:hover, .icon-btn:hover { color: var(--text); border-color: var(--amber-dim); }

.main { flex: 1; min-width: 0; display: flex; flex-direction: column; }
.topbar {
  display: flex; align-items: center; justify-content: space-between;
  padding: 14px 26px; border-bottom: 1px solid var(--line);
  background: var(--bg-panel); position: sticky; top: 0; z-index: 5;
}
.search-box {
  display: flex; align-items: center; gap: 8px;
  background: var(--bg-inset); border: 1px solid var(--line); border-radius: 20px;
  padding: 7px 14px; width: 320px; color: var(--text-faint);
}
.search-box input { background: none; border: none; outline: none; color: var(--text); width: 100%; }
.topbar-actions { display: flex; align-items: center; gap: 10px; }
.pill { font-family: var(--font-mono); font-size: .72rem; padding: 4px 10px; border-radius: 20px; border: 1px solid var(--line); color: var(--text-dim); }
.pill.free { color: var(--green); border-color: var(--green); }

.content { padding: 26px; flex: 1; }
.page-head { margin-bottom: 20px; }
.page-head .eyebrow { font-family: var(--font-mono); font-size: .72rem; letter-spacing: .1em; text-transform: uppercase; color: var(--amber); margin-bottom: 6px; }
.page-head p.lead { color: var(--text-dim); max-width: 760px; }

/* ===== Cards / grid ===== */
.grid { display: grid; gap: 16px; }
.grid.cols-4 { grid-template-columns: repeat(4, 1fr); }
.grid.cols-3 { grid-template-columns: repeat(3, 1fr); }
.grid.cols-2 { grid-template-columns: repeat(2, 1fr); }
@media (max-width: 1100px) { .grid.cols-4 { grid-template-columns: repeat(2, 1fr); } .grid.cols-3 { grid-template-columns: repeat(2, 1fr); } }
@media (max-width: 640px) { .grid.cols-4, .grid.cols-3, .grid.cols-2 { grid-template-columns: 1fr; } }

.card {
  background: var(--bg-panel); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 18px; position: relative; overflow: hidden;
}
.card.hover-link { cursor: pointer; transition: border-color .15s, transform .15s; }
.card.hover-link:hover { border-color: var(--amber-dim); transform: translateY(-2px); }
.card-icon { width: 38px; height: 38px; border-radius: 8px; background: var(--bg-panel-2); border: 1px solid var(--line); display: flex; align-items: center; justify-content: center; font-size: 1.1rem; margin-bottom: 12px; color: var(--amber); }
.card h4 { margin: 0 0 6px; font-family: var(--font-display); font-size: 1.15rem; }
.card p { color: var(--text-dim); font-size: .85rem; margin: 0; }
.card .tag { position: absolute; top: 14px; right: 14px; font-family: var(--font-mono); font-size: .62rem; padding: 2px 8px; border-radius: 10px; }
.tag.free { color: var(--green); border: 1px solid var(--green); }
.tag.premium { color: var(--amber); border: 1px solid var(--amber); }

/* ===== Forms ===== */
.field { margin-bottom: 14px; }
.field label { display: block; font-size: .78rem; color: var(--text-dim); margin-bottom: 5px; }
.field .hint { font-size: .72rem; color: var(--text-faint); margin-top: 4px; }
.input-row { display: flex; gap: 8px; }
input[type="number"], input[type="text"], select {
  width: 100%; padding: 9px 11px; background: var(--bg-inset);
  border: 1px solid var(--line); border-radius: var(--radius); color: var(--text);
  outline: none;
}
input[type="number"]:focus, input[type="text"]:focus, select:focus { border-color: var(--amber); }
select { appearance: none; }
.btn {
  padding: 10px 18px; border-radius: var(--radius); border: 1px solid var(--amber);
  background: var(--amber); color: #1a1206; font-weight: 600; cursor: pointer; font-size: .88rem;
}
.btn:hover { filter: brightness(1.08); }
.btn.secondary { background: transparent; color: var(--text); border-color: var(--line); }
.btn.secondary:hover { border-color: var(--text-dim); }
.btn.danger { background: transparent; border-color: var(--red); color: var(--red); }
.btn-row { display: flex; gap: 10px; margin-top: 6px; flex-wrap: wrap; }

.tabs { display: flex; gap: 4px; border-bottom: 1px solid var(--line); margin-bottom: 18px; flex-wrap: wrap; }
.tab { padding: 9px 14px; cursor: pointer; color: var(--text-dim); font-size: .85rem; border-bottom: 2px solid transparent; }
.tab.active { color: var(--amber); border-bottom-color: var(--amber); }

/* ===== Calculator layout ===== */
.calc-layout { display: grid; grid-template-columns: 1fr 1fr; gap: 20px; align-items: start; }
@media (max-width: 900px) { .calc-layout { grid-template-columns: 1fr; } }
.panel-title { font-family: var(--font-mono); font-size: .72rem; text-transform: uppercase; letter-spacing: .1em; color: var(--text-faint); margin-bottom: 12px; }

.readout {
  background: var(--bg-inset); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 20px; text-align: center; margin-bottom: 16px;
}
.readout .value { font-family: var(--font-mono); font-size: 2.4rem; color: var(--cyan); text-shadow: 0 0 18px rgba(53,208,192,.25); }
.readout .unit { font-family: var(--font-mono); color: var(--text-dim); font-size: 1rem; margin-left: 6px; }
.readout .label { color: var(--text-faint); font-size: .75rem; text-transform: uppercase; letter-spacing: .08em; margin-top: 6px; }

.formula-box {
  background: var(--bg-inset); border: 1px dashed var(--line); border-radius: var(--radius);
  padding: 12px 14px; font-family: var(--font-mono); font-size: .84rem; color: var(--text-dim); margin-bottom: 14px; overflow-x: auto; white-space: pre-wrap; word-break: break-word;
}

table { width: 100%; border-collapse: collapse; font-size: .85rem; }
th, td { text-align: left; padding: 9px 10px; border-bottom: 1px solid var(--line-soft); }
th { color: var(--text-faint); font-weight: 500; text-transform: uppercase; font-size: .68rem; letter-spacing: .06em; }
td.num { font-family: var(--font-mono); }
tr:hover td { background: var(--bg-panel-2); }

.badge { display: inline-block; padding: 2px 9px; border-radius: 10px; font-size: .72rem; font-family: var(--font-mono); }
.badge.normal { color: var(--green); border: 1px solid var(--green); }
.badge.warning { color: var(--amber); border: 1px solid var(--amber); }
.badge.high, .badge.low, .badge.out { color: var(--red); border: 1px solid var(--red); }
.badge.status-measured { color: var(--cyan); border: 1px solid var(--cyan); }
.badge.status-calculated { color: var(--green); border: 1px solid var(--green); }
.badge.status-estimated { color: var(--amber); border: 1px solid var(--amber); }
.badge.status-simulated { color: var(--blue); border: 1px solid var(--blue); }
.badge.status-predicted { color: var(--text-faint); border: 1px solid var(--text-faint); }

.disclaimer {
  font-size: .76rem; color: var(--text-faint); border-top: 1px solid var(--line);
  margin-top: 22px; padding-top: 14px; line-height: 1.6;
}
.assumptions-note { font-size: .74rem; color: var(--amber); background: rgba(232,163,61,.08); border: 1px solid var(--amber-dim); border-radius: var(--radius); padding: 8px 12px; margin-bottom: 14px; }

.result-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 10px 20px; margin-top: 8px; }
.result-item { display: flex; justify-content: space-between; padding: 7px 0; border-bottom: 1px solid var(--line-soft); font-size: .84rem; }
.result-item .k { color: var(--text-dim); }
.result-item .v { font-family: var(--font-mono); color: var(--text); }

.fl-card { padding: 16px; }
.fl-card h4 { color: var(--amber); }
.fl-meta { display: flex; gap: 8px; margin-bottom: 8px; }
.fl-cat { font-family: var(--font-mono); font-size: .65rem; text-transform: uppercase; color: var(--text-faint); border: 1px solid var(--line); border-radius: 10px; padding: 2px 8px; }
.fl-card .result-grid { grid-template-columns: 1fr; gap: 2px; }
.fl-card .result-item { flex-direction: column; align-items: flex-start; gap: 2px; padding: 8px 0; }
.fl-card .result-item .v { white-space: normal; word-break: break-word; text-align: left; }

.empty-state { text-align: center; padding: 50px 20px; color: var(--text-faint); }

footer.app-foot { padding: 16px 26px; border-top: 1px solid var(--line); color: var(--text-faint); font-size: .74rem; }

.pid-loop { display: flex; align-items: center; flex-wrap: wrap; gap: 0; font-family: var(--font-mono); font-size: .78rem; margin-bottom: 16px; }
.pid-loop .stage { background: var(--bg-panel-2); border: 1px solid var(--line); padding: 7px 12px; border-radius: var(--radius); color: var(--text-dim); }
.pid-loop .arrow { color: var(--amber); padding: 0 8px; }

.gauge-wrap { display: flex; justify-content: center; margin-bottom: 6px; }

.wizard-progress { display: flex; align-items: center; gap: 4px; margin-bottom: 22px; flex-wrap: wrap; }
.wizard-dot {
  width: 26px; height: 26px; border-radius: 50%; display: flex; align-items: center; justify-content: center;
  font-family: var(--font-mono); font-size: .68rem; border: 1px solid var(--line); color: var(--text-faint); background: var(--bg-panel-2); flex-shrink: 0;
}
.wizard-dot.done { background: var(--green); border-color: var(--green); color: #06210c; }
.wizard-dot.active { background: var(--amber); border-color: var(--amber); color: #1a1206; }
.wizard-connector { width: 14px; height: 1px; background: var(--line); flex-shrink: 0; }
.wizard-choice-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 12px; margin: 16px 0; }
.wizard-choice-card {
  padding: 18px; border: 1px solid var(--line); border-radius: var(--radius); background: var(--bg-panel-2);
  cursor: pointer; text-align: center; font-family: var(--font-display); font-size: 1.05rem;
}
.wizard-choice-card:hover { border-color: var(--amber); color: var(--amber); }
.wizard-choice-card.selected { border-color: var(--amber); background: rgba(232,163,61,.1); color: var(--amber); }

/* ---------- Support the Project ---------- */
.support-hero {
  max-width: 620px; margin: 0 auto; text-align: center; padding: 44px 36px;
  background: var(--bg-panel); border: 1px solid var(--line); border-radius: var(--radius);
}
.support-hero .heart { font-size: 2.1rem; margin-bottom: 6px; }
.support-hero h1 { font-size: 1.7rem; margin-bottom: 10px; }
.support-hero p { color: var(--text-dim); margin: 0 0 6px; font-size: .95rem; }
.support-hero .btn-donate {
  margin-top: 22px; padding: 15px 34px; font-size: 1.02rem; border-radius: 30px;
  background: linear-gradient(135deg, var(--amber), #c9762a); color: #1a1206; font-weight: 700;
  border: none; cursor: pointer; display: inline-flex; align-items: center; gap: 8px;
  box-shadow: 0 8px 22px rgba(232,163,61,.28);
}
.support-hero .btn-donate:hover { filter: brightness(1.06); }
.support-footer-sig { text-align: center; margin: 30px auto 0; max-width: 620px; color: var(--text-faint); font-size: .78rem; line-height: 1.7; border-top: 1px solid var(--line); padding-top: 18px; }
.support-footer-sig .name { color: var(--text-dim); font-family: var(--font-display); font-size: .95rem; }

.donate-modal-backdrop {
  position: fixed; inset: 0; background: rgba(5,8,12,.7); display: none;
  align-items: center; justify-content: center; padding: 20px; z-index: 200;
}
.donate-modal-backdrop.open { display: flex; }
.donate-modal {
  background: var(--bg-panel); border: 1px solid var(--line); border-radius: 12px;
  max-width: 420px; width: 100%; max-height: 90vh; overflow-y: auto; padding: 26px 24px 22px; position: relative;
  box-shadow: 0 24px 60px rgba(0,0,0,.5);
}
.donate-modal-close {
  position: absolute; top: 14px; right: 14px; width: 30px; height: 30px; border-radius: 50%;
  border: none; background: var(--bg-inset); color: var(--text-dim); font-size: 1.05rem; cursor: pointer;
  display: flex; align-items: center; justify-content: center;
}
.donate-modal-close:hover { background: var(--bg-panel-2); color: var(--text); }
.donate-modal h3 { font-size: 1.2rem; margin-bottom: 16px; }
.donate-amounts { display: grid; grid-template-columns: repeat(3, 1fr); gap: 8px; margin-bottom: 12px; }
.donate-amt {
  font-family: var(--font-mono); font-weight: 600; font-size: .92rem; padding: 12px 4px; text-align: center;
  border: 1.5px solid var(--line); border-radius: 8px; background: var(--bg-inset); cursor: pointer; color: var(--text);
}
.donate-amt.selected { border-color: var(--amber); background: rgba(232,163,61,.1); color: var(--amber); }
.donate-modal .field { margin-bottom: 14px; }
.qr-wrap { text-align: center; margin: 4px 0 12px; }
.qr-wrap img { border: 1px solid var(--line); border-radius: 8px; width: 190px; height: 190px; background: #fff; padding: 6px; margin: 0 auto 8px; }
.scan-pay-note { font-size: .8rem; color: var(--text-dim); text-align: center; margin-bottom: 16px; }
.upi-id-row {
  display: flex; justify-content: space-between; align-items: center; background: var(--bg-inset);
  border: 1px solid var(--line); border-radius: 8px; padding: 10px 12px; font-family: var(--font-mono); font-size: .86rem; margin-bottom: 16px;
}
.upi-id-row button { background: none; border: none; color: var(--amber); font-weight: 700; font-size: .76rem; cursor: pointer; }

.donate-success { text-align: center; padding: 10px 4px; }
.donate-success .big-heart {
  font-size: 3rem; display: inline-block; animation: heartPop .6s cubic-bezier(.34,1.56,.64,1);
}
.donate-success h3 { margin: 10px 0 8px; }
.donate-success p { color: var(--text-dim); font-size: .9rem; max-width: 320px; margin: 0 auto; }
@keyframes heartPop {
  0% { transform: scale(0); opacity: 0; }
  60% { transform: scale(1.25); opacity: 1; }
  100% { transform: scale(1); }
}
.confetti-dot {
  position: absolute; width: 7px; height: 7px; border-radius: 50%; opacity: 0;
  animation: confettiFall 1.1s ease-out forwards;
}
@keyframes confettiFall {
  0% { transform: translateY(0) scale(0); opacity: 1; }
  20% { transform: translateY(-10px) scale(1); opacity: 1; }
  100% { transform: translateY(60px) scale(.6); opacity: 0; }
}

/* ---------- Reviews & Ratings ---------- */
.review-summary { display: flex; align-items: center; gap: 24px; flex-wrap: wrap; }
.review-summary .avg-num { font-family: var(--font-mono); font-size: 2.4rem; color: var(--amber); line-height: 1; }
.review-summary .avg-meta { color: var(--text-dim); font-size: .82rem; }
.star-display { color: var(--amber); font-size: 1.1rem; letter-spacing: 2px; }
.star-display.small { font-size: .85rem; }
.star-input { display: flex; gap: 4px; font-size: 1.8rem; cursor: pointer; margin-bottom: 4px; }
.star-input .star { color: var(--line); transition: color .1s; }
.star-input .star.filled { color: var(--amber); }
.star-input .star:hover { transform: scale(1.08); }
.review-card { border-bottom: 1px solid var(--line-soft); padding: 16px 0; }
.review-card:last-child { border-bottom: none; }
.review-card-head { display: flex; justify-content: space-between; align-items: baseline; gap: 10px; flex-wrap: wrap; margin-bottom: 6px; }
.review-card-name { font-weight: 600; font-family: var(--font-display); }
.review-card-date { font-family: var(--font-mono); font-size: .72rem; color: var(--text-faint); }
.review-card-text { color: var(--text-dim); font-size: .88rem; line-height: 1.6; }

::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-thumb { background: var(--line); border-radius: 6px; }
::-webkit-scrollbar-track { background: transparent; }