/* ============================================
   CALVO SCIENTIFIC CALCULATOR + FORMULAS
   Screen-safe + 12 Themes + Formula Library
   ============================================ */

:root {
  --case-bg: #252529;
  --case-border: #3a3a42;
  --case-highlight: rgba(255,255,255,0.04);
  --case-shadow: rgba(0,0,0,0.5);
  --lcd-frame-bg: #1a1a1e;
  --lcd-bg: #9ab87a;
  --lcd-text: #1a2a10;
  --lcd-dim: #5a7a4a;
  --lcd-glow: rgba(154,184,122,0.15);
  --key-dark-top: #4a4a54;
  --key-dark-bot: #3a3a42;
  --key-dark-shadow: #2a2a30;
  --key-dark-text: #e8e8f0;
  --key-black-top: #2e2e36;
  --key-black-bot: #1e1e24;
  --key-black-shadow: #0e0e14;
  --key-black-text: #e8e8f0;
  --key-purple-top: #9a7ad8;
  --key-purple-bot: #7c5fb8;
  --key-purple-shadow: #5a3f98;
  --key-purple-text: #ffd700;
  --key-orange-top: #e8a04a;
  --key-orange-bot: #d4822a;
  --key-orange-shadow: #a0601a;
  --key-orange-text: #fff;
  --key-eq-top: #4a4a54;
  --key-eq-bot: #3a3a42;
  --key-eq-shadow: #2a2a30;
  --key-eq-text: #fff;
  --brand-orange: #ff8a1f;
  --brand-orange-deep: #d9650c;
  --accent: #ff8a1f;
}

/* ---------- 12 THEMES ---------- */
[data-theme="midnight"] {
  --case-bg: #1a1a20; --case-border: #2a2a34;
  --lcd-bg: #7a9a5a; --lcd-text: #0f1f08; --lcd-dim: #4a6a3a;
  --key-dark-top: #3a3a44; --key-dark-bot: #2a2a32; --key-dark-shadow: #1a1a22;
  --key-black-top: #26262e; --key-black-bot: #16161c; --key-black-shadow: #0a0a10;
  --key-purple-top: #8a6ac8; --key-purple-bot: #6c4fa8; --key-purple-shadow: #4a2f88;
  --key-orange-top: #d8903a; --key-orange-bot: #c4721a; --key-orange-shadow: #905010;
  --accent: #ff8a1f;
}
[data-theme="ocean"] {
  --case-bg: #1e2a3a; --case-border: #2e3a4a;
  --lcd-bg: #7ab8a0; --lcd-text: #0a2a1a; --lcd-dim: #4a7a60;
  --key-dark-top: #3a4a5a; --key-dark-bot: #2a3a4a; --key-dark-shadow: #1a2a3a;
  --key-black-top: #263040; --key-black-bot: #162030; --key-black-shadow: #0a1420;
  --key-purple-top: #5a8ad8; --key-purple-bot: #3a6ab8; --key-purple-shadow: #1a4a98;
  --key-purple-text: #a0d0ff;
  --key-orange-top: #e89040; --key-orange-bot: #c87020; --key-orange-shadow: #905010;
  --accent: #3a9aff;
}
[data-theme="rose"] {
  --case-bg: #2a1e24; --case-border: #3a2e34;
  --lcd-bg: #c8a8a0; --lcd-text: #2a0a0a; --lcd-dim: #8a6a60;
  --key-dark-top: #4a3e44; --key-dark-bot: #3a2e34; --key-dark-shadow: #2a1e24;
  --key-black-top: #2e2228; --key-black-bot: #1e1218; --key-black-shadow: #120a10;
  --key-purple-top: #c878a0; --key-purple-bot: #a85880; --key-purple-shadow: #883860;
  --key-purple-text: #ffd0e0;
  --key-orange-top: #e87860; --key-orange-bot: #c85840; --key-orange-shadow: #903820;
  --accent: #e8548b;
}
[data-theme="slate"] {
  --case-bg: #1b2230; --case-border: #2b3240;
  --lcd-bg: #8aa0b0; --lcd-text: #0a1420; --lcd-dim: #5a7080;
  --key-dark-top: #3a4250; --key-dark-bot: #2a3240; --key-dark-shadow: #1a2230;
  --key-black-top: #262e3c; --key-black-bot: #161e2c; --key-black-shadow: #0a121c;
  --key-purple-top: #6a8ad0; --key-purple-bot: #4a6ab0; --key-purple-shadow: #2a4a90;
  --key-purple-text: #a0c8ff;
  --key-orange-top: #e8a050; --key-orange-bot: #c88030; --key-orange-shadow: #905810;
  --accent: #5b9dff;
}
[data-theme="forest"] {
  --case-bg: #1a2a1e; --case-border: #2a3a2e;
  --lcd-bg: #8ab87a; --lcd-text: #0a1a08; --lcd-dim: #4a7a3a;
  --key-dark-top: #3a4a3e; --key-dark-bot: #2a3a2e; --key-dark-shadow: #1a2a1e;
  --key-black-top: #263a2a; --key-black-bot: #162a1e; --key-black-shadow: #0a1a12;
  --key-purple-top: #5ab85a; --key-purple-bot: #3a983a; --key-purple-shadow: #1a781a;
  --key-purple-text: #c0ffc0;
  --key-orange-top: #c8a840; --key-orange-bot: #a88820; --key-orange-shadow: #786010;
  --accent: #3fa34d;
}
[data-theme="grape"] {
  --case-bg: #221830; --case-border: #322840;
  --lcd-bg: #b8a0c8; --lcd-text: #1a0a2a; --lcd-dim: #786090;
  --key-dark-top: #4a3e5a; --key-dark-bot: #3a2e4a; --key-dark-shadow: #2a1e3a;
  --key-black-top: #362a44; --key-black-bot: #261a34; --key-black-shadow: #1a0e28;
  --key-purple-top: #a070d8; --key-purple-bot: #8050b8; --key-purple-shadow: #603098;
  --key-purple-text: #e0c0ff;
  --key-orange-top: #e8a050; --key-orange-bot: #c88030; --key-orange-shadow: #905810;
  --accent: #8a4fe0;
}
[data-theme="mint"] {
  --case-bg: #1a2a26; --case-border: #2a3a36;
  --lcd-bg: #80c8a8; --lcd-text: #0a1a14; --lcd-dim: #4a7a64;
  --key-dark-top: #3a4a46; --key-dark-bot: #2a3a36; --key-dark-shadow: #1a2a26;
  --key-black-top: #263a34; --key-black-bot: #162a24; --key-black-shadow: #0a1a16;
  --key-purple-top: #50b8a0; --key-purple-bot: #309880; --key-purple-shadow: #107860;
  --key-purple-text: #c0fff0;
  --key-orange-top: #d8a040; --key-orange-bot: #b88020; --key-orange-shadow: #885810;
  --accent: #1fbf9a;
}
[data-theme="ember"] {
  --case-bg: #2a1a16; --case-border: #3a2a26;
  --lcd-bg: #d0a080; --lcd-text: #1a0a04; --lcd-dim: #906050;
  --key-dark-top: #4a3a36; --key-dark-bot: #3a2a26; --key-dark-shadow: #2a1a16;
  --key-black-top: #3e2e28; --key-black-bot: #2e1e18; --key-black-shadow: #1a0e0a;
  --key-purple-top: #d87850; --key-purple-bot: #b85830; --key-purple-shadow: #983810;
  --key-purple-text: #ffd0b0;
  --key-orange-top: #e86040; --key-orange-bot: #c84020; --key-orange-shadow: #982010;
  --accent: #e34b3a;
}
[data-theme="sunflower"] {
  --case-bg: #2a2610; --case-border: #3a3620;
  --lcd-bg: #c8c070; --lcd-text: #1a1604; --lcd-dim: #888040;
  --key-dark-top: #4a4630; --key-dark-bot: #3a3620; --key-dark-shadow: #2a2610;
  --key-black-top: #3e3a24; --key-black-bot: #2e2a14; --key-black-shadow: #1a160a;
  --key-purple-top: #c8b040; --key-purple-bot: #a89020; --key-purple-shadow: #887010;
  --key-purple-text: #fff0a0;
  --key-orange-top: #d8a830; --key-orange-bot: #b88810; --key-orange-shadow: #886008;
  --accent: #e0b220;
}
[data-theme="coral"] {
  --case-bg: #2a1e1a; --case-border: #3a2e2a;
  --lcd-bg: #d0b0a0; --lcd-text: #1a0a06; --lcd-dim: #907060;
  --key-dark-top: #4a3e3a; --key-dark-bot: #3a2e2a; --key-dark-shadow: #2a1e1a;
  --key-black-top: #3e3228; --key-black-bot: #2e2218; --key-black-shadow: #1a120a;
  --key-purple-top: #d88860; --key-purple-bot: #b86840; --key-purple-shadow: #984820;
  --key-purple-text: #ffe0c0;
  --key-orange-top: #e87850; --key-orange-bot: #c85830; --key-orange-shadow: #983810;
  --accent: #ff7a54;
}
[data-theme="lavender"] {
  --case-bg: #221e2e; --case-border: #322e3e;
  --lcd-bg: #b8b0d0; --lcd-text: #120a1e; --lcd-dim: #787090;
  --key-dark-top: #4a465a; --key-dark-bot: #3a364a; --key-dark-shadow: #2a263a;
  --key-black-top: #363244; --key-black-bot: #262234; --key-black-shadow: #1a1628;
  --key-purple-top: #a090d8; --key-purple-bot: #8070b8; --key-purple-shadow: #605098;
  --key-purple-text: #e0d0ff;
  --key-orange-top: #d89860; --key-orange-bot: #b87840; --key-orange-shadow: #885820;
  --accent: #9b8ce0;
}

/* ============================================ */
* { box-sizing: border-box; margin: 0; padding: 0; -webkit-tap-highlight-color: transparent; }

html, body {
  width: 100%;
  height: 100vh;
  height: 100dvh;
  overflow: hidden;
  font-family: 'Inter', sans-serif;
  overscroll-behavior: none;
}

body {
  background: #0d0d10;
  color: #e8e8f0;
}

/* ---------- TOP NAVBAR ---------- */
.topbar {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 52px;
  background: rgba(18,18,22,0.95);
  backdrop-filter: blur(12px);
  border-bottom: 1px solid rgba(255,255,255,0.06);
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 0 16px;
  z-index: 200;
}

.topbar-brand {
  display: flex;
  align-items: center;
  gap: 8px;
}

.topbar-mark {
  width: 28px;
  height: 28px;
  border-radius: 7px;
  background: var(--brand-orange);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-family: 'JetBrains Mono', monospace;
  font-weight: 700;
  font-size: 0.72rem;
  box-shadow: 0 2px 0 var(--brand-orange-deep);
  flex-shrink: 0;
}

.topbar-name {
  font-size: 1rem;
  font-weight: 800;
  color: #e8e8f0;
  letter-spacing: 0.3px;
}

.topbar-tabs {
  display: flex;
  gap: 4px;
  background: rgba(255,255,255,0.05);
  border-radius: 10px;
  padding: 3px;
  overflow-x: auto;
  scrollbar-width: none;
  max-width: 62vw;
}
.topbar-tabs::-webkit-scrollbar { display: none; }

.topbar-tab {
  border: none;
  background: transparent;
  color: #888;
  font-family: 'Inter', sans-serif;
  font-weight: 600;
  font-size: 0.78rem;
  padding: 6px 14px;
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.2s ease;
  white-space: nowrap;
}

.topbar-tab:hover {
  color: #ccc;
}

.topbar-tab.active {
  background: var(--accent);
  color: #fff;
  box-shadow: 0 2px 8px rgba(0,0,0,0.3);
}

/* ---------- TOPBAR 3-DOT MENU ---------- */
.topbar-menu-wrap {
  position: relative;
  flex-shrink: 0;
  margin-left: 8px;
}

.topbar-menu-btn {
  width: 34px;
  height: 34px;
  border-radius: 9px;
  border: none;
  background: rgba(255,255,255,0.05);
  color: #aaa;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  transition: all 0.2s ease;
}
.topbar-menu-btn:hover {
  background: rgba(255,255,255,0.1);
  color: #fff;
}
.topbar-menu-btn:active { transform: scale(0.92); }

.topbar-menu {
  position: absolute;
  top: 42px;
  right: 0;
  min-width: 200px;
  background: var(--case-bg, #1e1e24);
  border: 1px solid var(--case-border, rgba(255,255,255,0.08));
  border-radius: 14px;
  padding: 6px;
  box-shadow: 0 20px 60px rgba(0,0,0,0.55);
  display: none;
  flex-direction: column;
  gap: 2px;
  z-index: 300;
  animation: slideUp 0.2s ease;
}
.topbar-menu.open { display: flex; }

.topbar-menu-item {
  display: flex;
  align-items: center;
  gap: 10px;
  border: none;
  background: transparent;
  color: #ddd;
  font-family: 'Inter', sans-serif;
  font-weight: 600;
  font-size: 0.82rem;
  padding: 10px 12px;
  border-radius: 9px;
  cursor: pointer;
  text-align: left;
  transition: all 0.15s ease;
}
.topbar-menu-item svg { flex-shrink: 0; color: var(--accent); }
.topbar-menu-item:hover { background: rgba(255,255,255,0.07); color: #fff; }

/* ---------- GENERIC APP MODAL ---------- */
.app-modal-overlay {
  position: fixed;
  inset: 0;
  background: rgba(0,0,0,0.6);
  display: none;
  align-items: center;
  justify-content: center;
  z-index: 400;
  padding: 16px;
}
.app-modal-overlay.open { display: flex; }

.app-modal {
  width: 100%;
  max-width: 380px;
  max-height: 80vh;
  overflow-y: auto;
  background: var(--case-bg, #1e1e24);
  border: 1px solid var(--case-border, rgba(255,255,255,0.08));
  border-radius: 16px;
  padding: 16px;
  box-shadow: 0 20px 60px rgba(0,0,0,0.6);
  animation: slideUp 0.25s ease;
}

.app-modal-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 14px;
  font-size: 0.78rem;
  font-weight: 700;
  color: #aaa;
  text-transform: uppercase;
  letter-spacing: 1px;
}

/* Languages */
.language-list {
  display: flex;
  flex-direction: column;
  gap: 6px;
}
.language-option {
  display: flex;
  align-items: center;
  justify-content: space-between;
  border: 1px solid rgba(255,255,255,0.06);
  background: rgba(255,255,255,0.03);
  color: #ddd;
  font-family: 'Inter', sans-serif;
  font-weight: 600;
  font-size: 0.86rem;
  padding: 12px 14px;
  border-radius: 10px;
  cursor: pointer;
  transition: all 0.15s ease;
}
.language-option:hover { background: rgba(255,255,255,0.07); }
.language-option.active {
  border-color: var(--accent);
  background: rgba(255,138,31,0.12);
  color: #fff;
}
.lang-check { color: var(--accent); font-weight: 800; }
.lang-soon {
  font-size: 0.65rem;
  color: #777;
  text-transform: uppercase;
  letter-spacing: 0.5px;
  font-weight: 700;
}

/* About */
.about-body {
  display: flex;
  flex-direction: column;
  gap: 12px;
  font-size: 0.86rem;
  line-height: 1.55;
  color: #cfcfd6;
}
.about-brand {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 2px;
}
.about-name { font-size: 1.05rem; font-weight: 800; color: #fff; }
.about-tag { font-size: 0.74rem; color: #999; }
.about-contact { color: #cfcfd6; }
.about-contact a { color: var(--accent); text-decoration: none; font-weight: 600; }
.about-contact a:hover { text-decoration: underline; }

/* ---------- TAB PANELS ---------- */
.tab-panel {
  display: none;
  width: 100%;
  height: calc(100vh - 52px);
  height: calc(100dvh - 52px);
  margin-top: 52px;
  overflow: hidden;
  animation: fadeIn 0.25s ease;
}

.tab-panel.active {
  display: flex;
  flex-direction: column;
}

@keyframes fadeIn {
  from { opacity: 0; }
  to { opacity: 1; }
}

/* ---------- CALCULATOR WRAP (screen-safe) ---------- */
.calc-wrap {
  flex: 1;
  min-height: 0;
  display: flex;
  justify-content: center;
  align-items: center;
  padding: 8px;
  overflow: hidden;
}

.calculator-case {
  background: var(--case-bg);
  border-radius: 16px;
  padding: 14px 12px 10px;
  /* Contain-fit: browser picks the largest size that respects the aspect
     ratio while staying within BOTH the width and height limits, so the
     calculator can never spill off any screen (phone, tablet, laptop). */
  width: min(400px, 92vw);
  height: min(760px, calc(100vh - 76px), calc(100dvh - 76px));
  aspect-ratio: 0.535;
  max-width: 92vw;
  max-height: min(calc(100vh - 76px), calc(100dvh - 76px));
  display: flex;
  flex-direction: column;
  position: relative;
  box-shadow:
    0 0 0 2px var(--case-border),
    0 0 0 4px rgba(0,0,0,0.3),
    0 20px 60px -10px var(--case-shadow),
    inset 0 1px 0 var(--case-highlight);
  transition: all 0.3s ease;
  overflow: hidden;
}

/* Solar Strip */
.solar-strip {
  position: absolute;
  top: 8px;
  right: 12px;
  display: flex;
  gap: 2px;
  padding: 2px;
  background: #1a1a1e;
  border-radius: 3px;
  border: 1px solid #333;
}
.solar-cell {
  width: 14px;
  height: 8px;
  background: linear-gradient(180deg, #2a2a30 0%, #1a1a1e 50%, #2a2a30 100%);
  border-radius: 1px;
}

/* Brand Row */
.brand-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0 2px 6px;
  margin-top: 2px;
  flex-shrink: 0;
}
.brand-left {
  display: flex;
  align-items: center;
  gap: 8px;
}
.brand-mark {
  width: 26px;
  height: 26px;
  border-radius: 6px;
  background: var(--brand-orange);
  display: flex;
  align-items: center;
  justify-content: center;
  color: #fff;
  font-family: 'JetBrains Mono', monospace;
  font-weight: 700;
  font-size: 0.68rem;
  box-shadow: 0 2px 0 var(--brand-orange-deep);
  flex-shrink: 0;
}
.brand-text { display: flex; flex-direction: column; }
.brand-name {
  color: #e8e8f0;
  font-size: 0.82rem;
  font-weight: 800;
  letter-spacing: 0.3px;
  line-height: 1.1;
}
.brand-tag {
  color: #888;
  font-size: 0.48rem;
  font-weight: 600;
  letter-spacing: 1px;
  text-transform: uppercase;
  margin-top: 1px;
}
.brand-right { text-align: right; flex-shrink: 0; }
.model-badge {
  color: var(--accent);
  font-size: 0.65rem;
  font-weight: 800;
  font-family: 'Orbitron', sans-serif;
  letter-spacing: 0.8px;
}
.model-tag {
  color: #666;
  font-size: 0.42rem;
  font-weight: 600;
  letter-spacing: 0.8px;
  margin-top: 1px;
}

/* LCD Display */
.lcd-frame {
  background: var(--lcd-frame-bg);
  border-radius: 8px;
  padding: 8px 8px;
  margin-bottom: 8px;
  box-shadow: inset 0 2px 8px rgba(0,0,0,0.5), 0 1px 0 rgba(255,255,255,0.03);
  flex-shrink: 0;
}
.lcd-bezel {
  background: var(--lcd-bg);
  border-radius: 4px;
  padding: 6px 8px;
  min-height: 56px;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  font-family: 'Orbitron', monospace;
  box-shadow: inset 0 1px 3px rgba(0,0,0,0.15), 0 0 16px var(--lcd-glow);
  position: relative;
  overflow: hidden;
}
.lcd-bezel::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 40%;
  background: linear-gradient(180deg, rgba(255,255,255,0.08) 0%, transparent 100%);
  pointer-events: none;
}
.lcd-top {
  display: flex;
  justify-content: space-between;
  align-items: center;
  font-size: 0.45rem;
  font-weight: 700;
  letter-spacing: 1px;
  margin-bottom: 2px;
}
.lcd-indicators { display: flex; gap: 5px; }
.indicator {
  color: var(--lcd-dim);
  transition: color 0.2s ease;
}
.indicator.active { color: var(--lcd-text); }
.indicator.ready { color: var(--lcd-dim); }
.lcd-sub {
  font-size: clamp(0.48rem, 2vw, 0.58rem);
  color: var(--lcd-dim);
  text-align: right;
  min-height: 10px;
  word-break: break-all;
  line-height: 1.2;
  margin-bottom: 1px;
}
.lcd-main {
  font-size: clamp(1rem, 5.5vw, 1.5rem);
  color: var(--lcd-text);
  text-align: right;
  font-weight: 500;
  letter-spacing: 2px;
  min-height: 24px;
  word-break: break-all;
  line-height: 1.15;
}

/* Mode Row */
.mode-row {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 8px;
  margin-bottom: 8px;
  flex-shrink: 0;
}
.mode-btn {
  padding: 5px 12px;
  border-radius: 6px;
  border: none;
  font-size: 0.48rem;
  font-weight: 700;
  font-family: 'Orbitron', sans-serif;
  letter-spacing: 1px;
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 3px;
  transition: all 0.15s ease;
  background: linear-gradient(180deg, var(--key-purple-top) 0%, var(--key-purple-bot) 100%);
  color: var(--key-purple-text);
  box-shadow: 0 3px 0 var(--key-purple-shadow), inset 0 1px 0 rgba(255,255,255,0.15);
  position: relative;
  overflow: hidden;
  white-space: nowrap;
}
.mode-btn::after {
  content: '';
  position: absolute;
  top: 0; left: -100%;
  width: 100%; height: 100%;
  background: linear-gradient(90deg, transparent, rgba(255,255,255,0.1), transparent);
  transition: left 0.4s ease;
}
.mode-btn:hover::after { left: 100%; }
.mode-btn:active {
  box-shadow: 0 1px 0 var(--key-purple-shadow), inset 0 2px 6px rgba(0,0,0,0.3);
  transform: translateY(2px);
}
.mode-btn.active {
  box-shadow: 0 1px 0 var(--key-purple-shadow), inset 0 2px 8px rgba(0,0,0,0.35);
  transform: translateY(2px);
  filter: brightness(1.15);
}
.mode-icon { font-size: 0.6rem; }

.replay-btn {
  width: 42px;
  height: 42px;
  border-radius: 50%;
  background: linear-gradient(180deg, var(--key-purple-top) 0%, var(--key-purple-bot) 100%);
  border: none;
  color: #fff;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0px;
  cursor: pointer;
  box-shadow: 0 3px 0 var(--key-purple-shadow), inset 0 1px 0 rgba(255,255,255,0.15);
  font-family: 'Orbitron', sans-serif;
  position: relative;
  transition: all 0.12s ease;
  flex-shrink: 0;
}
.replay-btn:active {
  box-shadow: 0 1px 0 var(--key-purple-shadow), inset 0 2px 6px rgba(0,0,0,0.3);
  transform: translateY(2px);
}
.replay-arrow { font-size: 0.45rem; line-height: 1; opacity: 0.8; }
.replay-text { font-size: 0.34rem; letter-spacing: 0.6px; font-weight: 700; }

/* Keypad */
.keypad {
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  grid-template-rows: repeat(8, 1fr);
  gap: 4px;
  width: 100%;
  flex: 1;
  min-height: 0;
}
.key {
  border-radius: 5px;
  border: none;
  font-family: 'JetBrains Mono', monospace;
  font-weight: 700;
  font-size: clamp(0.42rem, 2.6vw, 0.62rem);
  cursor: pointer;
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  line-height: 1.1;
  transition: all 0.08s ease;
  user-select: none;
  -webkit-user-select: none;
  overflow: hidden;
  padding: 0;
  min-width: 0;
  min-height: 0;
  width: 100%;
  height: 100%;
}
.key::before {
  content: '';
  position: absolute;
  top: 0; left: 0; right: 0;
  height: 45%;
  background: linear-gradient(180deg, rgba(255,255,255,0.08) 0%, transparent 100%);
  border-radius: 5px 5px 0 0;
  pointer-events: none;
}
.key:active { transform: translateY(2px); }

.key.dark {
  background: linear-gradient(180deg, var(--key-dark-top) 0%, var(--key-dark-bot) 100%);
  color: var(--key-dark-text);
  box-shadow: 0 3px 0 var(--key-dark-shadow), inset 0 1px 0 rgba(255,255,255,0.08);
}
.key.dark:active { box-shadow: 0 1px 0 var(--key-dark-shadow), inset 0 2px 6px rgba(0,0,0,0.3); }
.key.dark.num { font-size: clamp(0.55rem, 3.4vw, 0.8rem); }
.key.dark.op { font-size: clamp(0.6rem, 3.6vw, 0.88rem); }

.key.black {
  background: linear-gradient(180deg, var(--key-black-top) 0%, var(--key-black-bot) 100%);
  color: var(--key-black-text);
  box-shadow: 0 3px 0 var(--key-black-shadow), inset 0 1px 0 rgba(255,255,255,0.06);
  font-size: clamp(0.4rem, 2.4vw, 0.58rem);
}
.key.black:active { box-shadow: 0 1px 0 var(--key-black-shadow), inset 0 2px 6px rgba(0,0,0,0.4); }

.key.orange {
  background: linear-gradient(180deg, var(--key-orange-top) 0%, var(--key-orange-bot) 100%);
  color: var(--key-orange-text);
  box-shadow: 0 3px 0 var(--key-orange-shadow), inset 0 1px 0 rgba(255,255,255,0.15);
  font-size: clamp(0.42rem, 2.5vw, 0.6rem);
}
.key.orange:active { box-shadow: 0 1px 0 var(--key-orange-shadow), inset 0 2px 6px rgba(0,0,0,0.2); }

.key.purple {
  background: linear-gradient(180deg, var(--key-purple-top) 0%, var(--key-purple-bot) 100%);
  color: var(--key-purple-text);
  box-shadow: 0 3px 0 var(--key-purple-shadow), inset 0 1px 0 rgba(255,255,255,0.15);
  font-size: clamp(0.36rem, 2.2vw, 0.52rem);
}
.key.purple:active { box-shadow: 0 1px 0 var(--key-purple-shadow), inset 0 2px 6px rgba(0,0,0,0.3); }

.key.equals {
  background: linear-gradient(180deg, var(--key-eq-top) 0%, var(--key-eq-bot) 100%);
  color: var(--key-eq-text);
  box-shadow: 0 3px 0 var(--key-eq-shadow), inset 0 1px 0 rgba(255,255,255,0.08);
  font-size: clamp(0.65rem, 4vw, 0.92rem);
}
.key.equals:active { box-shadow: 0 1px 0 var(--key-eq-shadow), inset 0 2px 6px rgba(0,0,0,0.3); }

.shift-label {
  font-size: 0.36rem;
  color: #ffd700;
  position: absolute;
  top: 2px;
  left: 50%;
  transform: translateX(-50%);
  white-space: nowrap;
  font-weight: 700;
  z-index: 1;
}
.main-label {
  margin-top: 3px;
  z-index: 1;
}

.calc-footer {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 6px;
  margin-top: 8px;
  padding-top: 6px;
  border-top: 1px solid var(--case-border);
  font-size: 0.45rem;
  color: #555;
  font-weight: 600;
  letter-spacing: 1px;
  text-transform: uppercase;
  flex-shrink: 0;
}
.footer-dots { color: var(--accent); letter-spacing: 2px; }

/* ---------- FORMULAS TAB ---------- */
.formulas-wrap {
  flex: 1;
  display: flex;
  justify-content: center;
  padding: 12px;
  overflow: hidden;
}

.formulas-card {
  width: 100%;
  max-width: 600px;
  background: var(--case-bg);
  border: 1px solid var(--case-border);
  border-radius: 16px;
  padding: 20px;
  display: flex;
  flex-direction: column;
  max-height: 100%;
  overflow-y: auto;
  scrollbar-width: thin;
  scrollbar-color: var(--case-border) transparent;
  box-shadow: 0 20px 60px rgba(0,0,0,0.4);
}
.formulas-card::-webkit-scrollbar { width: 4px; }
.formulas-card::-webkit-scrollbar-thumb { background: var(--case-border); border-radius: 4px; }

.formulas-title {
  font-size: 1.1rem;
  font-weight: 800;
  color: #e8e8f0;
  margin-bottom: 2px;
}

.formulas-subtitle {
  font-size: 0.7rem;
  color: #888;
  margin-bottom: 14px;
  font-weight: 500;
}

.formula-search {
  width: 100%;
  padding: 11px 14px 11px 38px;
  border-radius: 12px;
  border: 1px solid var(--case-border);
  background: rgba(255,255,255,0.04) url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='none' stroke='%23777' stroke-width='2.2' stroke-linecap='round' stroke-linejoin='round'%3E%3Ccircle cx='11' cy='11' r='7'/%3E%3Cline x1='21' y1='21' x2='16.65' y2='16.65'/%3E%3C/svg%3E") no-repeat 12px center;
  background-size: 15px 15px;
  color: #e8e8f0;
  font-family: 'Inter', sans-serif;
  font-size: 0.85rem;
  margin-bottom: 12px;
  outline: none;
  box-shadow: 0 0 0 0 rgba(255,138,31,0);
  transition: border-color 0.2s, box-shadow 0.2s, background-color 0.2s;
}
.formula-search:hover {
  border-color: rgba(255,255,255,0.18);
}
.formula-search:focus {
  border-color: var(--accent);
  background-color: rgba(255,255,255,0.06);
  box-shadow: 0 0 0 3px rgba(255,138,31,0.15);
}
.formula-search::placeholder {
  color: #666;
}
/* Inputs/selects/passwords that reuse .formula-search but aren't a text
   search box (number fields, dropdowns, the AI key field) skip the icon. */
.formula-search.convert-input,
.formula-search.convert-select,
.formula-search.ai-key-input {
  padding-left: 14px;
  background-image: none;
}

.subject-pills {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  overflow-x: visible;
  padding-bottom: 8px;
  margin-bottom: 8px;
  scrollbar-width: none;
}
.subject-pills::-webkit-scrollbar { display: none; }

/* Converter category pills: wrap onto multiple lines instead of
   horizontally scrolling, so every category (including the last
   ones like Time/Data) is always fully visible, never cut off
   at the edge. */
#convertCategoryPills {
  flex-wrap: wrap;
  overflow-x: visible;
}

.subject-pill {
  flex-shrink: 0;
  padding: 7px 16px;
  border-radius: 20px;
  border: 1px solid var(--case-border);
  background: rgba(255,255,255,0.04);
  color: #aaa;
  font-family: 'Inter', sans-serif;
  font-weight: 600;
  font-size: 0.78rem;
  cursor: pointer;
  transition: all 0.2s ease;
  white-space: nowrap;
}
.subject-pill:hover {
  background: rgba(255,255,255,0.08);
  color: #ddd;
}
.subject-pill.active {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
  box-shadow: 0 2px 10px rgba(0,0,0,0.3);
}
.subject-pill.fav-pill {
  color: var(--accent);
  border-color: rgba(255,138,31,0.35);
}
.subject-pill.fav-pill.active {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}
.subject-pill.recent-pill {
  color: var(--accent);
  border-color: rgba(255,138,31,0.35);
}
.subject-pill.recent-pill.active {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}

.formula-list {
  flex: 1;
  overflow-y: auto;
  scrollbar-width: thin;
  scrollbar-color: var(--case-border) transparent;
  padding-right: 4px;
}
.formula-list::-webkit-scrollbar { width: 4px; }
.formula-list::-webkit-scrollbar-thumb { background: var(--case-border); border-radius: 4px; }

.formula-cat {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.65rem;
  text-transform: uppercase;
  letter-spacing: 0.1em;
  color: var(--accent);
  opacity: 0.9;
  font-weight: 700;
  padding: 14px 0 6px;
  border-top: 1px solid var(--case-border);
  margin-top: 6px;
}
.formula-cat:first-child {
  border-top: none;
  margin-top: 0;
  padding-top: 4px;
}

.formula-item {
  padding: 10px 12px;
  border-bottom: 1px solid rgba(255,255,255,0.04);
  transition: background 0.15s;
  border-radius: 6px;
}
.formula-item:hover {
  background: rgba(255,255,255,0.03);
}
.formula-item:last-child { border-bottom: none; }

.formula-item-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
}
.formula-item-text { flex: 1; min-width: 0; cursor: pointer; }
.formula-item-text:hover .formula-name { color: var(--accent); }
.formula-subj-tag {
  display: inline-block;
  font-size: 0.6rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--accent);
  background: rgba(255,255,255,0.06);
  border-radius: 4px;
  padding: 1px 6px;
  margin-right: 6px;
  vertical-align: middle;
}
.formula-item-actions {
  display: flex;
  align-items: center;
  gap: 2px;
  flex-shrink: 0;
}

.icon-action-btn {
  background: none;
  border: none;
  color: #777;
  cursor: pointer;
  font-size: 0.9rem;
  line-height: 1;
  padding: 6px;
  border-radius: 8px;
  transition: color 0.15s, background 0.15s;
}
.icon-action-btn:hover { color: #fff; background: rgba(255,255,255,0.08); }
.icon-action-btn:active { transform: translateY(1px); }
.fav-star-btn { font-size: 1.05rem; color: #888; }
.fav-star-btn.active { color: var(--accent); }

.formula-name {
  font-weight: 700;
  font-size: 0.85rem;
  color: #e0e0e8;
  margin-bottom: 3px;
}

.formula-expr {
  font-family: 'JetBrains Mono', monospace;
  color: var(--accent);
  font-size: 0.82rem;
  opacity: 0.85;
  line-height: 1.4;
}

.formula-empty {
  text-align: center;
  padding: 40px 0;
  color: #666;
  font-size: 0.85rem;
}

/* ---------- SHARED APP CARD BITS (history/convert/percentage) ---------- */
.app-card-header {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 10px;
  margin-bottom: 12px;
}

.pill-btn {
  flex-shrink: 0;
  padding: 7px 14px;
  border-radius: 20px;
  border: 1px solid var(--case-border);
  background: rgba(255,255,255,0.05);
  color: #ccc;
  font-family: 'Inter', sans-serif;
  font-weight: 600;
  font-size: 0.72rem;
  cursor: pointer;
  transition: all 0.15s ease;
  white-space: nowrap;
}
.pill-btn:hover { background: rgba(255,255,255,0.1); color: #fff; }
.pill-btn:active { transform: translateY(1px); }
.pill-btn.small { padding: 5px 10px; font-size: 0.65rem; }
.pill-btn.save-btn {
  display: block;
  width: 100%;
  margin: 10px 0 14px;
  text-align: center;
  background: linear-gradient(135deg, var(--accent), var(--brand-orange-deep));
  color: #fff;
  border: none;
  font-weight: 700;
  padding: 10px;
}

/* ---------- HISTORY TAB ---------- */
.history-item {
  padding: 10px 12px;
  border-bottom: 1px solid rgba(255,255,255,0.04);
  border-radius: 6px;
  transition: background 0.15s;
}
.history-item:hover { background: rgba(255,255,255,0.04); }
.history-item-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
}
.history-item-text { flex: 1; min-width: 0; cursor: pointer; }
.history-expr {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.78rem;
  color: #999;
  word-break: break-all;
}
.history-result {
  font-family: 'JetBrains Mono', monospace;
  font-size: 1rem;
  font-weight: 700;
  color: var(--accent);
  word-break: break-all;
}
.history-time {
  font-size: 0.6rem;
  color: #666;
  margin-top: 2px;
}

/* ---------- CONVERTER TAB ---------- */
.convert-row {
  display: flex;
  align-items: flex-start;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 4px;
}
.convert-field {
  flex: 1 1 130px;
  display: flex;
  flex-direction: column;
  gap: 6px;
  min-width: 0;
}
.convert-input, .convert-select {
  margin-bottom: 0 !important;
  width: 100%;
  min-width: 0;
}
.convert-select {
  max-width: 100%;
  color-scheme: dark;
  background: rgba(255,255,255,0.06);
  color: #e8e8f0;
  -webkit-appearance: menulist;
  appearance: menulist;
}
.convert-input {
  font-family: 'JetBrains Mono', monospace;
  font-weight: 700;
  font-size: 0.95rem;
}
.convert-swap {
  flex-shrink: 0;
  border-radius: 50%;
  width: 38px;
  height: 38px;
  padding: 0;
  font-size: 1.1rem;
  display: flex;
  align-items: center;
  justify-content: center;
  align-self: center;
}
.convert-hint {
  margin-top: 14px;
  font-size: 0.72rem;
  color: #777;
  text-align: center;
}

/* On narrow screens stack From/To vertically with the swap button
   centered between them, so neither field ever gets squeezed
   off-screen next to the round swap button. */
@media (max-width: 420px) {
  .convert-row {
    flex-direction: column;
    align-items: stretch;
  }
  .convert-field {
    flex: 1 1 auto;
    width: 100%;
  }
  .convert-swap {
    align-self: center;
    margin: 2px 0;
  }
}

/* ---------- PERCENTAGE TAB ---------- */
.percent-panel { margin-top: 6px; }
.percent-block {
  background: rgba(255,255,255,0.03);
  border: 1px solid var(--case-border);
  border-radius: 10px;
  padding: 12px;
  margin-bottom: 10px;
}
.percent-label {
  font-size: 0.82rem;
  color: #ccc;
  line-height: 2.2;
}
.pinput {
  width: 68px;
  padding: 5px 8px;
  border-radius: 6px;
  border: 1px solid var(--case-border);
  background: rgba(255,255,255,0.06);
  color: #fff;
  font-family: 'JetBrains Mono', monospace;
  font-weight: 700;
  font-size: 0.8rem;
  margin: 0 4px;
  text-align: center;
}
.percent-eq {
  display: inline-block;
  margin-left: 8px;
  color: var(--accent);
  font-weight: 700;
}

/* ---------- GRADE PERCENTAGE (subject list) ---------- */
.grade-subject-list {
  display: flex;
  flex-direction: column;
  gap: 10px;
  margin-bottom: 14px;
}
.grade-subject-row {
  display: flex;
  align-items: center;
  gap: 8px;
  background: rgba(255,255,255,0.04);
  border: 1px solid var(--case-border);
  border-radius: 12px;
  padding: 12px 14px;
}
.grade-subject-name {
  flex: 1 1 auto;
  min-width: 0;
  font-size: 0.8rem;
  color: #aaa;
  font-weight: 600;
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
}
.grade-input {
  width: 56px;
  flex-shrink: 0;
  padding: 7px 6px;
  border-radius: 8px;
  border: 1px solid var(--case-border);
  background: rgba(255,255,255,0.06);
  color: #fff;
  font-family: 'JetBrains Mono', monospace;
  font-weight: 700;
  font-size: 0.85rem;
  text-align: center;
  outline: none;
}
.grade-input:focus { border-color: var(--accent); }
.grade-slash {
  flex-shrink: 0;
  color: #777;
  font-weight: 700;
}
.grade-remove-btn {
  flex-shrink: 0;
  width: 26px;
  height: 26px;
  border-radius: 50%;
  border: none;
  background: transparent;
  color: #888;
  font-size: 1rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.15s ease;
}
.grade-remove-btn:hover { background: rgba(255,80,80,0.15); color: #ff6b6b; }

.add-subject-btn {
  display: block;
  width: 100%;
  text-align: center;
  background: transparent;
  border: none;
  color: var(--accent);
  font-weight: 700;
  font-size: 0.85rem;
  padding: 10px;
  margin-bottom: 14px;
}
.add-subject-btn:hover { background: rgba(255,138,31,0.08); }

.grade-result-box {
  background: linear-gradient(135deg, var(--accent), var(--brand-orange-deep));
  color: #fff;
  border-radius: 14px;
  padding: 18px;
  text-align: center;
  font-size: 1.8rem;
  font-weight: 800;
  font-family: 'JetBrains Mono', monospace;
  margin-bottom: 4px;
}

/* ---------- CGPA TABLE ---------- */
.cgpa-scale-row {
  display: flex;
  align-items: center;
  gap: 8px;
  margin-bottom: 10px;
  font-size: 0.78rem;
  color: #aaa;
}
.cgpa-scale-row select { margin-bottom: 0; flex: 1; }
.cgpa-table {
  display: flex;
  flex-direction: column;
  gap: 6px;
  margin-bottom: 10px;
}
.cgpa-row {
  display: grid;
  grid-template-columns: 2fr 1fr 1fr auto;
  gap: 6px;
  align-items: center;
}
.cgpa-row input, .cgpa-row select {
  width: 100%;
  padding: 7px 8px;
  border-radius: 6px;
  border: 1px solid var(--case-border);
  background: rgba(255,255,255,0.06);
  color: #fff;
  font-family: 'Inter', sans-serif;
  font-size: 0.75rem;
}
.cgpa-row .cgpa-del {
  background: rgba(255,90,90,0.15);
  color: #ff8080;
  border: none;
  border-radius: 6px;
  width: 26px;
  height: 26px;
  cursor: pointer;
  font-size: 0.8rem;
}
.cgpa-semester-label {
  display: block;
  width: 100%;
  font-size: 0.7rem;
  letter-spacing: 0.04em;
  color: var(--accent);
  font-weight: 700;
  margin-top: 6px;
  background: transparent;
  border: none;
  border-bottom: 1px dashed rgba(255,255,255,0.18);
  padding: 4px 2px 6px;
  font-family: 'Inter', sans-serif;
}
.cgpa-semester-label::placeholder { color: var(--accent); opacity: 0.7; }
.cgpa-semester-label:focus { outline: none; border-bottom-color: var(--accent); }
.cgpa-trend-result {
  text-align: center;
  font-family: 'Orbitron', sans-serif;
  font-size: 0.95rem;
  font-weight: 800;
  color: var(--accent);
  padding: 8px;
  background: rgba(255,255,255,0.03);
  border-radius: 10px;
  margin: 8px 0 4px;
}
.gpa-trend { font-size: 0.7rem; }
.gpa-trend-up { color: #4dd88a; }
.gpa-trend-down { color: #ff8080; }
.gpa-trend-flat { color: #888; }
.cgpa-actions {
  display: flex;
  gap: 8px;
  margin-bottom: 10px;
  flex-wrap: wrap;
}
.cgpa-result {
  text-align: center;
  font-family: 'Orbitron', sans-serif;
  font-size: 1.3rem;
  font-weight: 800;
  color: var(--accent);
  padding: 10px;
  background: rgba(255,255,255,0.03);
  border-radius: 10px;
  margin-bottom: 4px;
}

.saved-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 6px;
  padding-top: 10px;
  border-top: 1px solid var(--case-border);
  font-size: 0.75rem;
  color: #aaa;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
}
.saved-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 9px 10px;
  border-bottom: 1px solid rgba(255,255,255,0.04);
  border-radius: 6px;
  font-size: 0.8rem;
}
.saved-item .saved-del {
  background: none;
  border: none;
  color: #888;
  cursor: pointer;
  font-size: 0.85rem;
  padding: 2px 6px;
}
.saved-item .saved-del:hover { color: #ff8080; }

.convert-attribution {
  text-align: center;
  font-size: 0.62rem;
  color: #666;
  margin-top: 8px;
}

/* ---------- AI SOLVER TAB ---------- */
.ai-key-box {
  background: rgba(255,255,255,0.03);
  border: 1px solid var(--case-border);
  border-radius: 14px;
  padding: 14px 14px 12px;
  margin-bottom: 16px;
}
.ai-key-row {
  display: flex;
  align-items: center;
  gap: 8px;
}
.ai-key-input {
  flex: 1 1 auto;
  min-width: 0;
  margin-bottom: 0;
  font-family: 'JetBrains Mono', monospace;
  letter-spacing: 0.03em;
}
#aiKeyToggleBtn { flex-shrink: 0; }
.ai-key-actions {
  margin-top: 10px;
}
.ai-key-link {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  color: var(--accent);
  font-size: 0.76rem;
  font-weight: 600;
  text-decoration: none;
  border-bottom: 1px dashed rgba(255,138,31,0.4);
  transition: opacity 0.15s;
}
.ai-key-link::before {
  content: "🔑";
  font-size: 0.8rem;
}
.ai-key-link:hover { opacity: 0.8; }
.ai-key-status {
  font-size: 0.72rem;
  font-weight: 600;
  margin-top: 8px;
  min-height: 1em;
}
.ai-key-status.ok { color: #5fd97a; }
.ai-key-status.err { color: #ff6b6b; }

.ai-solver-box { display: flex; flex-direction: column; }

.ai-question-input {
  width: 100%;
  resize: vertical;
  min-height: 70px;
  padding: 12px 14px;
  border-radius: 12px;
  border: 1px solid var(--case-border);
  background: rgba(255,255,255,0.04);
  color: #e8e8f0;
  font-family: 'Inter', sans-serif;
  font-size: 0.85rem;
  line-height: 1.5;
  margin-bottom: 12px;
  outline: none;
  box-shadow: 0 0 0 0 rgba(255,138,31,0);
  transition: border-color 0.2s, box-shadow 0.2s, background-color 0.2s;
}
.ai-question-input:hover { border-color: rgba(255,255,255,0.18); }
.ai-question-input:focus {
  border-color: var(--accent);
  background-color: rgba(255,255,255,0.06);
  box-shadow: 0 0 0 3px rgba(255,138,31,0.15);
}
.ai-question-input::placeholder { color: #666; }

.ai-image-row {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
  margin-bottom: 10px;
}
.ai-image-filename {
  font-size: 0.72rem;
  color: #999;
  overflow: hidden;
  text-overflow: ellipsis;
  white-space: nowrap;
  max-width: 160px;
}
#aiVoiceBtn.listening {
  background: rgba(255,70,70,0.18);
  color: #ff6b6b;
  border-color: rgba(255,70,70,0.5);
  animation: aiVoicePulse 1.3s ease-in-out infinite;
}
@keyframes aiVoicePulse {
  0%, 100% { box-shadow: 0 0 0 0 rgba(255,70,70,0.35); }
  50% { box-shadow: 0 0 0 8px rgba(255,70,70,0); }
}
.ai-image-preview {
  display: block;
  max-width: 100%;
  max-height: 180px;
  border-radius: 12px;
  border: 1px solid var(--case-border);
  margin-bottom: 12px;
  object-fit: contain;
}

.ai-solver-actions {
  display: flex;
  gap: 8px;
  margin-bottom: 4px;
}
.ai-solver-actions .save-btn { margin: 0; flex: 1 1 auto; }
.ai-solver-actions #aiRefreshBtn,
.ai-solver-actions #aiSaveBtn { flex-shrink: 0; }

.ai-result-box:empty { display: none; }
.ai-result-card {
  background: rgba(255,255,255,0.03);
  border: 1px solid var(--case-border);
  border-radius: 14px;
  padding: 16px;
  margin: 14px 0;
  font-size: 0.85rem;
  line-height: 1.6;
  color: #d8d8e0;
}
.ai-loading {
  color: var(--accent);
  font-weight: 600;
  display: inline-flex;
  align-items: center;
  gap: 8px;
}
.ai-loading::before {
  content: "";
  width: 13px;
  height: 13px;
  border-radius: 50%;
  border: 2px solid rgba(255,138,31,0.3);
  border-top-color: var(--accent);
  animation: ai-spin 0.7s linear infinite;
}
@keyframes ai-spin { to { transform: rotate(360deg); } }
.ai-error {
  color: #ff6b6b;
  font-weight: 600;
}
.ai-step {
  padding: 10px 0;
  border-top: 1px solid rgba(255,255,255,0.06);
}
.ai-step:first-child { border-top: none; padding-top: 0; }
.ai-step-label {
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--accent);
  font-weight: 700;
  margin-bottom: 4px;
}
.ai-step-body {
  color: #ccc;
  font-size: 0.85rem;
}
.ai-list {
  margin: 6px 0 10px 18px;
  padding: 0;
}
.ai-list li {
  margin-bottom: 4px;
  color: #ccc;
}
.ai-answer {
  margin-top: 12px;
  padding: 12px 14px;
  border-radius: 12px;
  background: linear-gradient(135deg, var(--accent), var(--brand-orange-deep));
  color: #fff;
  font-weight: 700;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.95rem;
}
.ai-answer-label {
  font-family: 'Inter', sans-serif;
  font-weight: 700;
  text-transform: uppercase;
  font-size: 0.68rem;
  letter-spacing: 0.06em;
  opacity: 0.85;
  margin-right: 4px;
}

.ai-saved-header { margin-top: 8px; }
.ai-saved-title {
  font-size: 0.75rem;
  color: #aaa;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  margin: 0;
}
.ai-saved-item {
  position: relative;
  padding: 10px 34px 10px 12px;
  border-bottom: 1px solid rgba(255,255,255,0.04);
  border-radius: 8px;
  transition: background 0.15s;
}
.ai-saved-item:hover { background: rgba(255,255,255,0.03); }
.ai-saved-question {
  font-weight: 700;
  font-size: 0.82rem;
  color: #e0e0e8;
  margin-bottom: 3px;
}
.ai-saved-answer {
  font-family: 'JetBrains Mono', monospace;
  color: var(--accent);
  font-size: 0.8rem;
  opacity: 0.9;
  margin-bottom: 3px;
}
.ai-saved-time {
  font-size: 0.62rem;
  color: #666;
}
.ai-saved-delete {
  position: absolute;
  top: 8px;
  right: 6px;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  border: none;
  background: transparent;
  color: #888;
  font-size: 0.8rem;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  transition: all 0.15s ease;
}
.ai-saved-delete:hover { background: rgba(255,80,80,0.15); color: #ff6b6b; }

.confirm-armed {
  background: rgba(255,80,80,0.15) !important;
  border-color: rgba(255,80,80,0.4) !important;
  color: #ff8080 !important;
}

/* ---------- THEME FAB ---------- */
.theme-fab {
  position: fixed;
  bottom: 20px;
  right: 20px;
  width: 44px;
  height: 44px;
  border-radius: 50%;
  background: linear-gradient(135deg, var(--accent), var(--brand-orange-deep));
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  cursor: pointer;
  box-shadow: 0 4px 20px rgba(0,0,0,0.4), 0 0 0 3px rgba(255,255,255,0.08);
  transition: all 0.25s ease;
  z-index: 100;
  border: none;
}
.theme-fab:hover {
  transform: scale(1.1) rotate(15deg);
  box-shadow: 0 6px 25px rgba(0,0,0,0.5), 0 0 0 3px rgba(255,255,255,0.12);
}
.theme-fab:active { transform: scale(0.95); }

/* ---------- THEME PANEL ---------- */
.theme-panel {
  position: fixed;
  bottom: 72px;
  right: 12px;
  left: 12px;
  max-width: 360px;
  margin: 0 auto;
  background: var(--case-bg);
  border: 1px solid var(--case-border);
  border-radius: 16px;
  padding: 14px;
  box-shadow: 0 20px 60px rgba(0,0,0,0.6);
  display: none;
  z-index: 101;
  animation: slideUp 0.25s ease;
}
@keyframes slideUp {
  from { opacity: 0; transform: translateY(10px); }
  to { opacity: 1; transform: none; }
}
.theme-panel.open { display: block; }

.theme-panel-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 12px;
  font-size: 0.72rem;
  font-weight: 700;
  color: #aaa;
  text-transform: uppercase;
  letter-spacing: 1px;
}
.theme-close {
  background: none;
  border: none;
  color: #666;
  font-size: 0.9rem;
  cursor: pointer;
  padding: 2px 6px;
  border-radius: 4px;
  transition: all 0.15s;
}
.theme-close:hover { color: #fff; background: rgba(255,255,255,0.1); }

.theme-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 10px;
}

.theme-option {
  aspect-ratio: 0.85;
  border-radius: 10px;
  border: 2px solid transparent;
  cursor: pointer;
  position: relative;
  overflow: hidden;
  transition: all 0.2s ease;
  display: flex;
  flex-direction: column;
  padding: 5px 4px 4px;
  gap: 3px;
  background: #1a1a1e;
}
.theme-option:hover { transform: scale(1.06); }
.theme-option.active {
  border-color: var(--accent);
  box-shadow: 0 0 0 2px var(--case-bg), 0 0 0 3px var(--accent);
}
.theme-mini-lcd {
  height: 14px;
  border-radius: 2px;
  margin-bottom: 1px;
  opacity: 0.9;
}
.theme-mini-keys {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 2px;
  flex: 1;
}
.theme-mini-key {
  height: 6px;
  border-radius: 2px;
}
.theme-mini-key.accent { opacity: 1; }
.theme-label {
  font-size: 0.48rem;
  text-align: center;
  margin-top: 2px;
  font-weight: 600;
  color: #888;
  letter-spacing: 0.3px;
}

/* ---------- RESPONSIVE ----------
   Font sizes on keys/LCD use clamp() so they scale continuously with the
   calculator's actual rendered size (which itself is fit to the viewport
   via aspect-ratio contain-scaling above). These breakpoints only tweak
   spacing/max-width — not font sizes — so there's no fixed-size step that
   could overflow on an in-between screen size. */
@media (min-width: 500px) {
  .calculator-case { padding: 16px 14px 12px; }
  .mode-btn { padding: 6px 14px; font-size: 0.52rem; }
  .replay-btn { width: 46px; height: 46px; }
}

@media (min-width: 768px) {
  .calculator-case { padding: 18px 16px 14px; }
}

@media (max-width: 360px) {
  .keypad { gap: 3px; }
  .theme-grid { gap: 6px; }
  .topbar-tab { padding: 5px 10px; font-size: 0.72rem; }
}

@media (max-height: 700px) {
  .calc-wrap { padding: 4px; }
  .calculator-case { padding: 10px 10px 8px; }
  .lcd-frame { padding: 6px 6px; margin-bottom: 6px; }
  .mode-row { margin-bottom: 6px; gap: 6px; }
  .calc-footer { margin-top: 6px; padding-top: 4px; }
}

/* Very short screens (landscape phones, small laptops in split view):
   let the aspect ratio relax so the case gets wider/shorter instead of
   the height constraint squeezing it into an unreadably thin sliver. */
@media (max-height: 480px) {
  .calculator-case { aspect-ratio: 0.85; width: min(560px, 92vw); }
}

/* Animations */
@keyframes pulse-glow {
  0%, 100% { box-shadow: 0 0 16px var(--lcd-glow); }
  50% { box-shadow: 0 0 24px var(--lcd-glow), 0 0 40px var(--lcd-glow); }
}
.lcd-bezel.pulse { animation: pulse-glow 2s ease infinite; }

/* ---------- TOAST (share/copy feedback) ---------- */
.app-toast {
  position: fixed;
  left: 50%;
  bottom: 28px;
  transform: translateX(-50%) translateY(12px);
  background: #1c1c20;
  color: #f0f0f0;
  border: 1px solid var(--case-border);
  padding: 10px 18px;
  border-radius: 24px;
  font-family: 'Inter', sans-serif;
  font-size: 0.8rem;
  font-weight: 600;
  box-shadow: 0 6px 24px rgba(0,0,0,0.4);
  opacity: 0;
  pointer-events: none;
  z-index: 9999;
  transition: opacity 0.2s ease, transform 0.2s ease;
  max-width: 88vw;
  text-align: center;
}
.app-toast.show {
  opacity: 1;
  transform: translateX(-50%) translateY(0);
}
/* Visually hidden but accessible to screen readers & search engines */
.sr-only{
  position:absolute;
  width:1px; height:1px;
  padding:0; margin:-1px;
  overflow:hidden;
  clip:rect(0,0,0,0);
  white-space:nowrap;
  border:0;
}