:root {
  --bg: #f3f8ff;
  --bg-soft: #ecf4ff;
  --surface: #ffffff;
  --surface-soft: #f9fcff;
  --text: #10243a;
  --muted: #506982;
  --brand: #0f766e;
  --brand-strong: #0b5f59;
  --accent: #d97706;
  --warn: #b45309;
  --border: #d4e2f0;
  --border-strong: #c2d5e8;
  --shadow-sm: 0 8px 18px rgba(16, 36, 58, 0.08);
  --shadow-md: 0 14px 28px rgba(16, 36, 58, 0.12);
  --shadow-lg: 0 24px 48px rgba(16, 36, 58, 0.16);
}

* {
  box-sizing: border-box;
}

html,
body {
  min-height: 100%;
}

body {
  margin: 0;
  color: var(--text);
  font-family: "Source Sans 3", sans-serif;
  background:
    radial-gradient(circle at 8% -6%, rgba(15, 118, 110, 0.18), transparent 32%),
    radial-gradient(circle at 92% 0%, rgba(217, 119, 6, 0.2), transparent 28%),
    linear-gradient(180deg, var(--bg-soft), var(--bg));
}

h1,
h2,
h3 {
  margin: 0;
  font-family: "Nunito", sans-serif;
  letter-spacing: 0.01em;
}

p,
ol {
  margin-top: 0;
}

.topbar {
  position: sticky;
  top: 0;
  z-index: 30;
  padding: 1rem 1.3rem;
  border-bottom: 1px solid var(--border);
  background: rgba(255, 255, 255, 0.9);
  backdrop-filter: blur(10px);
}

.brand-wrap {
  display: flex;
  align-items: center;
  gap: 0.95rem;
}

.brand-mark {
  width: 3.1rem;
  height: 3.1rem;
  border-radius: 0.95rem;
  display: grid;
  place-items: center;
  font-weight: 800;
  color: #fff;
  background: linear-gradient(145deg, #16a34a, #0f766e 58%, #155e75);
  box-shadow: var(--shadow-md);
}

.subhead {
  margin: 0.2rem 0 0;
  color: var(--muted);
}

.main-nav {
  display: grid;
  align-content: start;
  gap: 0.55rem;
  padding: 1rem;
  border: 1px solid var(--border);
  border-radius: 1.1rem;
  background: rgba(255, 255, 255, 0.9);
  box-shadow: var(--shadow-sm);
  position: sticky;
  top: 5.3rem;
  height: fit-content;
}

.nav-btn {
  border: 1px solid var(--border);
  background: rgba(255, 255, 255, 0.9);
  color: var(--text);
  border-radius: 999px;
  padding: 0.55rem 1rem;
  font-weight: 700;
  cursor: pointer;
  transition: transform 130ms ease, box-shadow 130ms ease;
  width: 100%;
  text-align: left;
}

.nav-btn:hover {
  transform: translateY(-1px);
  box-shadow: var(--shadow-sm);
}

.nav-btn.active {
  color: #fff;
  border-color: transparent;
  background: linear-gradient(145deg, var(--brand), var(--brand-strong));
}

.app-shell {
  max-width: 1240px;
  margin: 0 auto;
  padding: 1rem 1.3rem 2rem;
  display: grid;
  grid-template-columns: 250px minmax(0, 1fr);
  gap: 1rem;
}

.container {
  max-width: none;
  margin: 0;
  padding: 0;
}

.panel {
  display: none;
  position: relative;
  overflow: hidden;
  border: 1px solid var(--border);
  border-radius: 1.15rem;
  padding: 1.2rem;
  background: rgba(255, 255, 255, 0.86);
  box-shadow: var(--shadow-sm);
  animation: panelIn 220ms ease;
}

.panel::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 4px;
  background: linear-gradient(90deg, var(--brand), var(--accent));
  opacity: 0.7;
}

.panel.active {
  display: block;
}

@keyframes panelIn {
  from {
    opacity: 0;
    transform: translateY(8px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.card,
.list-item {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 1rem;
  box-shadow: var(--shadow-sm);
}

.panel-soft {
  padding: 1rem;
}

.panel-soft + .panel-soft {
  margin-top: 0.9rem;
}

.list {
  display: grid;
  gap: 0.95rem;
}

.pack-group {
  border: 1px solid var(--border-strong);
  border-radius: 1rem;
  padding: 0.9rem;
  background: linear-gradient(180deg, #ffffff, var(--surface-soft));
}

.pack-title {
  margin: 0 0 0.7rem;
  color: var(--brand-strong);
  font-size: 1.02rem;
}

.list-item {
  padding: 1rem;
  transition: transform 130ms ease, box-shadow 130ms ease;
}

.list-item.clickable-deck {
  cursor: pointer;
}

.list-item:hover {
  transform: translateY(-2px);
  box-shadow: var(--shadow-md);
}

.mydeck-actions {
  margin: 0 0 0.8rem;
}

.list-title {
  margin: 0 0 0.3rem;
}

.muted {
  color: var(--muted);
}

.toolbar,
.row {
  display: flex;
  align-items: center;
}

.toolbar {
  gap: 0.65rem;
  margin: 0 0 1rem;
  padding: 0.75rem;
  border: 1px solid var(--border);
  border-radius: 0.9rem;
  background: #fff;
}

.row.between {
  justify-content: space-between;
}

.row.center {
  justify-content: center;
}

.row.wrap {
  flex-wrap: wrap;
}

.row.gap {
  gap: 0.65rem;
}

.form label {
  display: grid;
  gap: 0.35rem;
  margin-bottom: 0.8rem;
  font-weight: 700;
}

input,
select,
textarea,
button {
  font: inherit;
}

input,
select,
textarea {
  border: 1px solid var(--border);
  border-radius: 0.78rem;
  padding: 0.62rem 0.75rem;
  background: #fff;
  color: var(--text);
}

input:focus,
select:focus,
textarea:focus,
button:focus {
  outline: 3px solid rgba(15, 118, 110, 0.2);
  outline-offset: 1px;
}

.grid.two-col {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.85rem;
}

.stack {
  display: grid;
  gap: 0.85rem;
  margin-bottom: 1rem;
}

.card-input {
  border: 1px solid var(--border);
  border-radius: 1rem;
  padding: 0.82rem;
  background: linear-gradient(180deg, #ffffff, #f6fbff);
}

.designer-grid {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  gap: 0.85rem;
  margin-bottom: 0.65rem;
}

.designer-face {
  border: 1px solid var(--border);
  border-radius: 1rem;
  min-height: 164px;
  padding: 0.8rem;
  background:
    radial-gradient(circle at 90% 14%, rgba(15, 118, 110, 0.1), transparent 40%),
    linear-gradient(165deg, #ffffff, #eef9f7);
}

.designer-label {
  display: block;
  margin-bottom: 0.5rem;
  color: var(--brand-strong);
  font-weight: 800;
}

.designer-edit {
  min-height: 96px;
  border: 1px dashed #a9cbc4;
  border-radius: 0.72rem;
  padding: 0.62rem;
  background: rgba(255, 255, 255, 0.95);
  white-space: pre-wrap;
  outline: 0;
}

.designer-edit:focus {
  border-color: var(--brand);
  box-shadow: 0 0 0 3px rgba(15, 118, 110, 0.16);
}

.designer-tip {
  margin: 0 0 0.65rem;
  font-size: 0.9rem;
  color: var(--muted);
}

.designer-attach-row {
  margin-top: 0.55rem;
  display: flex;
  gap: 0.45rem;
  align-items: center;
  flex-wrap: wrap;
}

.btn.small {
  padding: 0.36rem 0.62rem;
  font-size: 0.82rem;
}

.attach-btn {
  cursor: pointer;
}

.designer-file-name {
  font-size: 0.83rem;
  color: var(--muted);
}

.designer-image-preview {
  margin-top: 0.55rem;
  width: 100%;
  max-height: 160px;
  object-fit: contain;
  border: 1px solid var(--border);
  border-radius: 0.72rem;
  background: #fff;
}

.btn {
  border: 0;
  border-radius: 0.78rem;
  padding: 0.6rem 1rem;
  font-weight: 800;
  color: #fff;
  cursor: pointer;
  background: linear-gradient(145deg, var(--brand), var(--brand-strong));
  box-shadow: 0 7px 14px rgba(15, 118, 110, 0.24);
  transition: transform 130ms ease, opacity 130ms ease, box-shadow 130ms ease;
}

.btn:hover {
  transform: translateY(-1px);
}

.btn:active {
  transform: translateY(0);
  opacity: 0.92;
}

.btn.secondary {
  background: #e7eff8;
  color: var(--text);
  box-shadow: none;
}

.btn.warn {
  background: linear-gradient(145deg, #d97706, #b45309);
  box-shadow: 0 7px 14px rgba(180, 83, 9, 0.24);
}

.pill {
  display: inline-block;
  margin: 0 0 0.45rem;
  padding: 0.18rem 0.58rem;
  border-radius: 999px;
  font-size: 0.84rem;
  font-weight: 700;
  color: var(--brand-strong);
  background: #e3f6f1;
}

.warning-text {
  color: #8a3513;
  font-weight: 800;
}

.import-notice {
  margin: 0 0 0.8rem;
  padding: 0.65rem 0.85rem;
  border: 1px solid #bfe6da;
  border-radius: 0.8rem;
  background: #ecfbf5;
  color: #0f5f4e;
  font-weight: 700;
}

.hidden {
  display: none !important;
}

.stat-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
  gap: 0.8rem;
  margin-bottom: 1rem;
}

.stat-card {
  padding: 0.95rem;
  text-align: center;
  border: 1px solid var(--border);
  background: linear-gradient(180deg, #ffffff, #f4f9ff);
}

.nav-stat {
  width: 100%;
  cursor: pointer;
  transition: transform 130ms ease, box-shadow 130ms ease, border-color 130ms ease;
}

.nav-stat:hover {
  transform: translateY(-2px);
  border-color: var(--brand);
  box-shadow: var(--shadow-md);
}

.stat-value {
  display: block;
  margin-bottom: 0.15rem;
  font-size: 1.7rem;
  font-weight: 800;
  color: var(--brand-strong);
}

.modal {
  position: fixed;
  inset: 0;
  z-index: 40;
  padding: 1rem;
  display: grid;
  place-items: center;
  background: rgba(16, 36, 58, 0.58);
}

.modal-content {
  width: min(980px, 100%);
  max-height: 95vh;
  overflow: auto;
  border: 1px solid var(--border-strong);
  border-radius: 1.1rem;
  padding: 1rem;
  background: linear-gradient(180deg, #ffffff, #f7fbff);
  box-shadow: var(--shadow-lg);
}

.progress-wrap {
  height: 0.78rem;
  margin: 0.6rem 0 1rem;
  border-radius: 999px;
  overflow: hidden;
  background: #e5edf5;
}

.progress-fill {
  width: 0;
  height: 100%;
  background: linear-gradient(90deg, #10b981, #0f766e);
  transition: width 200ms ease;
}

.flashcard {
  width: 100%;
  border: 0;
  background: transparent;
  padding: 0;
  margin: 0.45rem 0 1rem;
}

.study-card-wrap {
  display: grid;
  grid-template-columns: 64px minmax(0, 1fr) 64px;
  align-items: center;
  gap: 0.8rem;
}

.study-arrow {
  height: 64px;
  width: 64px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: #ffffff;
  color: var(--brand-strong);
  font-weight: 800;
  font-size: 1.15rem;
  cursor: pointer;
  box-shadow: var(--shadow-sm);
  transition: transform 120ms ease, box-shadow 120ms ease, border-color 120ms ease;
}

.study-arrow:hover {
  transform: translateY(-1px);
  border-color: var(--brand);
  box-shadow: var(--shadow-md);
}

.face {
  width: 100%;
  min-height: 320px;
  border-radius: 1.1rem;
  border: 1px solid var(--border-strong);
  padding: 1.25rem;
  display: grid;
  place-items: center;
  text-align: center;
  line-height: 1.35;
  font-size: clamp(1.28rem, 3vw, 1.8rem);
  font-weight: 800;
  font-family: "STIX Two Math", "Cambria Math", "Noto Sans Math", "Segoe UI Symbol", "DejaVu Sans", "Arial Unicode MS", "Source Sans 3", sans-serif;
  background:
    radial-gradient(circle at 12% 14%, rgba(217, 119, 6, 0.14), transparent 34%),
    radial-gradient(circle at 88% 86%, rgba(15, 118, 110, 0.14), transparent 40%),
    linear-gradient(165deg, #ffffff, #eef8ff);
  box-shadow: var(--shadow-md);
  backface-visibility: hidden;
}

.face-content {
  width: 100%;
  display: grid;
  gap: 0.6rem;
  justify-items: center;
}

.face-image {
  max-width: 100%;
  max-height: 240px;
  object-fit: contain;
  border: 1px solid var(--border);
  border-radius: 0.6rem;
  background: #fff;
}

.face-text {
  margin: 0;
  white-space: pre-wrap;
  word-break: break-word;
}

.face.flipped {
  animation: readableFlip 280ms ease;
}

@keyframes readableFlip {
  0% {
    transform: rotateY(0deg) scale(1);
  }
  50% {
    transform: rotateY(90deg) scale(0.98);
  }
  100% {
    transform: rotateY(0deg) scale(1);
  }
}

.toast {
  position: fixed;
  right: 1rem;
  bottom: 1rem;
  z-index: 50;
  border-radius: 0.8rem;
  padding: 0.7rem 0.95rem;
  color: #fff;
  background: #172c45;
  box-shadow: var(--shadow-md);
}

@media (max-width: 960px) {
  .app-shell {
    grid-template-columns: 1fr;
  }

  .grid.two-col,
  .designer-grid {
    grid-template-columns: 1fr;
  }

  .toolbar {
    flex-wrap: wrap;
  }

  .main-nav {
    position: static;
    display: flex;
    flex-wrap: wrap;
    padding: 0.75rem;
  }

  .nav-btn {
    width: auto;
    text-align: center;
  }
}

@media (max-width: 640px) {
  .topbar,
  .app-shell {
    padding-left: 0.85rem;
    padding-right: 0.85rem;
  }

  .main-nav {
    padding: 0.7rem;
  }

  .toolbar {
    flex-direction: column;
    align-items: stretch;
  }

  .btn {
    width: 100%;
  }

  .nav-btn {
    width: 100%;
    text-align: left;
  }

  .panel {
    padding: 0.95rem;
  }

  .study-card-wrap {
    grid-template-columns: 50px minmax(0, 1fr) 50px;
    gap: 0.55rem;
  }

  .study-arrow {
    width: 50px;
    height: 50px;
  }
}