:root {
  font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
}

body {
  margin: 0;
  min-height: 100vh;
  background: var(--page-gradient);
  color: var(--text-primary);
  transition: background 0.3s ease, color 0.3s ease;
  --page-gradient: radial-gradient(circle at top left, #0f172a, #020617 55%);
  --text-primary: #e2e8f0;
  --text-muted: #94a3b8;
  --surface-bg: rgba(15, 23, 42, 0.85);
  --surface-shadow: 0 20px 45px rgba(2, 6, 23, 0.35);
  --input-bg: rgba(15, 23, 42, 0.75);
  --input-border: rgba(148, 163, 184, 0.45);
  --input-text: #e2e8f0;
  --card-bg: rgba(15, 23, 42, 0.75);
  --card-border: rgba(96, 165, 250, 0.35);
  --hint-color: #cbd5f5;
  --counter-color: #cbd5f5;
  --table-border: rgba(148, 163, 184, 0.3);
  --table-header-bg: rgba(30, 41, 59, 0.75);
  --table-row-bg: rgba(15, 23, 42, 0.65);
  --footer-color: #94a3b8;
  --button-primary-bg: linear-gradient(120deg, #3f87ff, #7f5cff);
  --button-primary-text: #fff;
  --button-secondary-bg: rgba(30, 41, 59, 0.85);
  --button-secondary-text: #e2e8f0;
  --button-secondary-border: rgba(148, 163, 184, 0.4);
  --button-danger-bg: rgba(220, 38, 38, 0.12);
  --button-danger-border: rgba(248, 113, 113, 0.35);
  --button-danger-text: #f87171;
  --control-shadow: 0 2px 8px rgba(2, 6, 23, 0.25);
  --version-color: #ffffff;
  --topbar-bg: rgba(15, 23, 42, 0.82);
  --topbar-border: rgba(148, 163, 184, 0.25);
  --topbar-shadow: 0 18px 45px rgba(2, 6, 23, 0.3);
}

body[data-theme="dark"] {
  color-scheme: dark;
}

body[data-theme="light"] {
  --page-gradient: linear-gradient(145deg, rgba(79, 105, 231, 0.1), rgba(255, 255, 255, 0.85));
  --text-primary: #1f2430;
  --text-muted: #465063;
  --surface-bg: rgba(255, 255, 255, 0.9);
  --surface-shadow: 0 20px 45px rgba(46, 54, 80, 0.08);
  --input-bg: #fff;
  --input-border: rgba(88, 99, 126, 0.3);
  --input-text: #1f2430;
  --card-bg: #fff;
  --card-border: rgba(63, 135, 255, 0.25);
  --hint-color: #4f5d78;
  --counter-color: #465063;
  --table-border: rgba(88, 99, 126, 0.2);
  --table-header-bg: rgba(79, 105, 231, 0.08);
  --table-row-bg: rgba(255, 255, 255, 0.6);
  --footer-color: #4f5d78;
  --button-secondary-bg: #fff;
  --button-secondary-text: #3f4860;
  --button-secondary-border: rgba(88, 99, 126, 0.3);
  --button-danger-bg: rgba(239, 68, 68, 0.12);
  --button-danger-border: rgba(248, 113, 113, 0.55);
  --button-danger-text: #dc2626;
  --control-shadow: 0 2px 8px rgba(46, 54, 80, 0.08);
  color-scheme: light;
  --version-color: #000000;
  --topbar-bg: rgba(255, 255, 255, 0.9);
  --topbar-border: rgba(88, 99, 126, 0.18);
  --topbar-shadow: 0 18px 35px rgba(46, 54, 80, 0.14);
}

.top-bar {
  position: sticky;
  top: 0;
  z-index: 20;
  background: var(--topbar-bg);
  border-bottom: 1px solid var(--topbar-border);
  box-shadow: var(--topbar-shadow);
  backdrop-filter: blur(18px);
  -webkit-backdrop-filter: blur(18px);
  padding: 0.75rem 1.5rem;
}

.top-bar__inner {
  max-width: 1080px;
  margin: 0 auto;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1.5rem;
}

.top-bar__brand {
  display: flex;
  align-items: center;
  gap: 0.65rem;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
}

.top-bar__logo {
  font-size: 1.4rem;
}

.top-bar__title {
  font-size: 1.05rem;
}

.top-bar__brand {
  cursor: pointer;
  transition: opacity 0.2s ease;
}

.top-bar__brand:hover {
  opacity: 0.8;
}

.top-bar__actions {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.top-bar__status {
  font-size: 0.85rem;
  color: var(--text-muted);
  transition: color 0.3s ease;
  margin-right: 0.5rem;
}

.top-bar__status[data-state="success"],
.top-bar__status[data-state="authenticated"] {
  color: #34d399;
}

.top-bar__status[data-state="error"] {
  color: #fca5a5;
}

.top-bar__status[data-state="info"] {
  color: #60a5fa;
}

.top-bar__buttons {
  display: flex;
  gap: 0.5rem;
}

.top-bar__buttons button {
  flex: 0 0 auto;
  min-width: 90px;
}

main {
  max-width: 1080px;
  margin: 0 auto;
  padding: 2.5rem 1.5rem 4rem;
}

header {
  text-align: center;
  margin-bottom: 2.5rem;
  position: relative;
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
  align-items: center;
}

.hero-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  justify-content: center;
}

.hero-actions button {
  min-width: 190px;
}

h1 {
  font-size: clamp(2.25rem, 5vw, 3rem);
  margin-bottom: 0.5rem;
}

p.subtitle {
  margin: 0 auto;
  max-width: 640px;
  font-size: 1.05rem;
  line-height: 1.6;
  color: var(--text-muted);
}

section {
  background: var(--surface-bg);
  border-radius: 18px;
  box-shadow: var(--surface-shadow);
  padding: 2rem;
  margin-bottom: 1.75rem;
  backdrop-filter: blur(8px);
}

h2 {
  font-size: 1.5rem;
  margin-top: 0;
}

h3 {
  margin-top: 0;
}

ul {
  padding-left: 1.25rem;
  line-height: 1.7;
}

label {
  display: block;
  margin-bottom: 0.75rem;
  font-weight: 600;
}

input[type="file"],
input[type="text"],
select,
textarea,
button {
  font: inherit;
  padding: 0.65rem 0.85rem;
  border-radius: 10px;
  border: 1px solid var(--input-border);
  background-color: var(--input-bg);
  color: var(--input-text);
  box-shadow: var(--control-shadow);
  transition: transform 0.15s ease, box-shadow 0.15s ease, background 0.3s ease, color 0.3s ease;
  width: 100%;
  box-sizing: border-box;
}

input[type="file"],
input[type="text"],
select,
textarea {
  color: var(--input-text);
}

input::placeholder,
textarea::placeholder {
  color: var(--text-muted);
}

textarea {
  min-height: 90px;
  resize: vertical;
}

button {
  cursor: pointer;
  background: var(--button-primary-bg);
  border: none;
  color: var(--button-primary-text);
  font-weight: 600;
  letter-spacing: 0.02em;
  width: auto;
}

button:hover {
  transform: translateY(-1px);
  box-shadow: 0 12px 25px rgba(63, 135, 255, 0.2);
}

button:disabled {
  opacity: 0.6;
  cursor: not-allowed;
  transform: none;
  box-shadow: none;
}

button:disabled:hover {
  transform: none;
  box-shadow: none;
}

button.secondary {
  background: var(--button-secondary-bg);
  color: var(--button-secondary-text);
  border: 1px solid var(--button-secondary-border);
}

button.danger {
  background: var(--button-danger-bg);
  color: var(--button-danger-text);
  border: 1px solid var(--button-danger-border);
}

button.secondary:hover {
  background: rgba(148, 163, 184, 0.15);
}

button.danger:hover {
  background: rgba(220, 38, 38, 0.18);
}

.theme-toggle__icon {
  font-size: 1.1rem;
  margin-right: 0.3rem;
}

.theme-toggle__label {
  font-size: 0.85rem;
  font-weight: 600;
}

button#themeToggle {
  display: inline-flex;
  align-items: center;
  width: auto;
  min-width: 120px;
}

button.download-example {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding-inline: 1rem;
}

.flex-row {
  display: flex;
  gap: 1rem;
  flex-wrap: wrap;
}

.flex-row > * {
  flex: 1 1 240px;
}

.section-header {
  margin-bottom: 1.5rem;
}

.account-card {
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
  padding: 1.5rem;
  border-radius: 16px;
  background: rgba(15, 23, 42, 0.6);
  border: 1px solid rgba(148, 163, 184, 0.25);
  position: relative;
  overflow: hidden;
}

body[data-theme="light"] .account-card {
  background: rgba(255, 255, 255, 0.9);
  border-color: rgba(79, 105, 231, 0.18);
}

.account-card__hint {
  margin: 0;
  font-size: 0.9rem;
  line-height: 1.5;
  color: var(--text-muted);
}

.account-card.is-loading::after {
  content: '';
  position: absolute;
  inset: 0;
  background: rgba(15, 23, 42, 0.6);
  backdrop-filter: blur(4px);
  z-index: 2;
}

body[data-theme="light"] .account-card.is-loading::after {
  background: rgba(255, 255, 255, 0.65);
}

.account-card.is-loading::before {
  content: '';
  position: absolute;
  top: 50%;
  left: 50%;
  width: 44px;
  height: 44px;
  border-radius: 999px;
  border: 4px solid transparent;
  border-top-color: #7f5cff;
  border-right-color: #7f5cff;
  transform: translate(-50%, -50%);
  animation: spinner 0.9s linear infinite;
  z-index: 3;
}

.account-status {
  font-weight: 600;
  padding: 0.75rem 1rem;
  border-radius: 12px;
  border: 1px solid rgba(148, 163, 184, 0.35);
  background: rgba(148, 163, 184, 0.18);
  color: var(--text-muted);
  transition: background 0.3s ease, color 0.3s ease, border 0.3s ease;
}

.account-status--success {
  background: rgba(34, 197, 94, 0.18);
  border-color: rgba(34, 197, 94, 0.45);
  color: #4ade80;
}

.account-status--error {
  background: rgba(248, 113, 113, 0.2);
  border-color: rgba(248, 113, 113, 0.45);
  color: #fca5a5;
}

.account-status--info {
  background: rgba(59, 130, 246, 0.15);
  border-color: rgba(59, 130, 246, 0.35);
  color: #93c5fd;
}

body[data-theme="light"] .account-status--success {
  color: #15803d;
  background: rgba(34, 197, 94, 0.18);
}

body[data-theme="light"] .account-status--error {
  color: #b91c1c;
  background: rgba(248, 113, 113, 0.18);
}

body[data-theme="light"] .account-status--info {
  color: #1d4ed8;
  background: rgba(59, 130, 246, 0.15);
}

.account-form {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

.account-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
}

.account-actions button {
  flex: 1 1 180px;
}

.auth-main {
  max-width: 520px;
  margin: 0 auto;
  padding: 4rem 1.5rem;
  min-height: calc(100vh - 80px);
  display: flex;
  align-items: center;
  justify-content: center;
}

.auth-container {
  width: 100%;
  text-align: center;
}

.auth-container h1 {
  margin-bottom: 0.5rem;
}

.auth-container .subtitle {
  margin-bottom: 2rem;
}

.auth-form {
  background: var(--surface-bg);
  border-radius: 18px;
  box-shadow: var(--surface-shadow);
  padding: 2rem;
  margin-bottom: 1.5rem;
  backdrop-filter: blur(8px);
  display: flex;
  flex-direction: column;
  gap: 1.25rem;
  text-align: left;
}

.auth-form label {
  display: block;
  margin-bottom: 0;
}

.auth-form button[type="submit"] {
  margin-top: 0.5rem;
}

.auth-footer {
  color: var(--text-muted);
}

.auth-footer p {
  margin: 0;
}

.link-button {
  background: none;
  border: none;
  color: #3f87ff;
  cursor: pointer;
  text-decoration: underline;
  padding: 0;
  font-weight: 600;
  width: auto;
  box-shadow: none;
}

.link-button:hover {
  color: #7f5cff;
  transform: none;
  box-shadow: none;
}

.features {
  margin-top: 2rem;
}

.features h2 {
  text-align: center;
  margin-bottom: 2rem;
  font-size: 2rem;
}

.features-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  gap: 1.5rem;
}

.feature-card {
  background: var(--surface-bg);
  border-radius: 18px;
  box-shadow: var(--surface-shadow);
  padding: 2rem;
  text-align: center;
  backdrop-filter: blur(8px);
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.feature-card:hover {
  transform: translateY(-4px);
  box-shadow: 0 24px 50px rgba(2, 6, 23, 0.45);
}

.feature-icon {
  font-size: 3rem;
  margin-bottom: 1rem;
}

.feature-card h3 {
  margin: 0.5rem 0;
  font-size: 1.25rem;
}

.feature-card p {
  margin: 0;
  color: var(--text-muted);
  line-height: 1.6;
}

.hidden {
  display: none !important;
}

.page {
  display: block;
}

.page.hidden {
  display: none;
}

.card {
  text-align: center;
  font-size: clamp(1.5rem, 3vw, 2rem);
  padding: 2.5rem 2rem;
  border-radius: 20px;
  border: 2px solid var(--card-border);
  background: var(--card-bg);
  box-shadow: 0 18px 35px rgba(2, 6, 23, 0.35);
  min-height: 240px;
  display: flex;
  align-items: center;
  justify-content: center;
  white-space: pre-wrap;
  line-height: 1.6;
}

.card__hint {
  color: var(--hint-color);
  font-size: 0.95rem;
  margin-top: 1rem;
  min-height: 1.5rem;
}

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  margin-top: 1.5rem;
  justify-content: center;
}

.progress-meter {
  margin-top: 1.75rem;
}

.progress-meter__label {
  text-transform: uppercase;
  letter-spacing: 0.08em;
  font-size: 0.8rem;
  margin-bottom: 0.75rem;
  color: var(--counter-color);
  text-align: center;
}

.progress-meter__track {
  position: relative;
  height: 10px;
  border-radius: 999px;
  background: rgba(148, 163, 184, 0.25);
  overflow: hidden;
}

.progress-meter__fill {
  position: absolute;
  top: 0;
  left: 0;
  height: 100%;
  width: 0;
  border-radius: inherit;
  background: linear-gradient(120deg, rgba(63, 135, 255, 0.9), rgba(127, 92, 255, 0.9));
  background-size: 200% 200%;
  animation: shimmer 3s ease infinite;
  transition: width 0.5s ease;
}

@keyframes spinner {
  from {
    transform: translate(-50%, -50%) rotate(0deg);
  }
  to {
    transform: translate(-50%, -50%) rotate(360deg);
  }
}

@keyframes shimmer {
  0% {
    background-position: 0% 50%;
  }
  50% {
    background-position: 100% 50%;
  }
  100% {
    background-position: 0% 50%;
  }
}

.set-controls {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin-bottom: 1.5rem;
}

.sets-list {
  display: grid;
  gap: 1rem;
}

.set-card {
  border: 1px solid rgba(148, 163, 184, 0.2);
  border-radius: 14px;
  padding: 1.25rem;
  background: rgba(15, 23, 42, 0.55);
  display: flex;
  flex-direction: column;
  gap: 1rem;
}

body[data-theme="light"] .set-card {
  background: rgba(255, 255, 255, 0.8);
}

.set-card__header {
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.set-card__meta {
  color: var(--text-muted);
  font-size: 0.9rem;
}

.set-card__actions {
  display: flex;
  gap: 0.75rem;
  flex-wrap: wrap;
}

.set-card__actions button {
  flex: 1 1 140px;
}

.column-chip {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.4rem 0.75rem;
  border-radius: 999px;
  background: rgba(148, 163, 184, 0.25);
  margin: 0 0.5rem 0.5rem 0;
  font-size: 0.9rem;
}

.column-chip button {
  width: auto;
  padding: 0.15rem 0.4rem;
  border-radius: 999px;
  font-size: 0.75rem;
}

.column-editor,
.templates-editor,
.cards-editor {
  margin-top: 1.5rem;
}

.cards-editor table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.95rem;
  min-width: 480px;
}

.cards-editor th,
.cards-editor td {
  border: 1px solid var(--table-border);
  padding: 0.5rem;
  text-align: left;
}

.cards-editor th {
  background: var(--table-header-bg);
}

.cards-editor tbody tr:nth-child(even) {
  background: var(--table-row-bg);
}

.cards-editor input {
  width: 100%;
}

.cards-editor__table-wrapper {
  overflow-x: auto;
}

.study-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  margin-bottom: 1.5rem;
  flex-wrap: wrap;
}

.back-button {
  width: auto;
}

.empty-state {
  text-align: center;
  color: var(--text-muted);
}

footer {
  text-align: center;
  color: var(--footer-color);
  font-size: 0.85rem;
  margin-top: 3rem;
}

.version-badge {
  position: fixed;
  bottom: 0.75rem;
  right: 0.75rem;
  font-size: 0.7rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--version-color);
  opacity: 0.7;
  pointer-events: none;
}

.confetti-container {
  pointer-events: none;
  position: fixed;
  inset: 0;
  overflow: hidden;
  z-index: 1000;
}

.confetti-container.active {
  display: block;
}

.confetti-piece {
  position: absolute;
  display: block;
  width: 12px;
  height: 18px;
  top: 0;
  will-change: transform, opacity;
}

@media (max-width: 900px) {
  .top-bar__inner {
    flex-wrap: wrap;
    gap: 0.75rem;
  }

  .top-bar__actions {
    width: 100%;
    flex-wrap: wrap;
    gap: 0.75rem;
  }

  .top-bar__status {
    width: 100%;
    margin-right: 0;
  }

  .top-bar__buttons {
    flex: 1;
  }

  .top-bar__buttons button {
    min-width: 80px;
  }
  
  button#themeToggle {
    min-width: 100px;
  }
}

@media (max-width: 520px) {
  .hero-actions button {
    flex: 1 1 100%;
  }

  .top-bar {
    padding: 0.65rem 1rem;
  }

  .top-bar__buttons button {
    flex: 1 1 100%;
  }
}

@media (max-width: 720px) {
  main {
    padding: 2rem 1rem 3rem;
  }

  section {
    padding: 1.75rem 1.25rem;
  }

  .card {
    padding: 2rem 1.5rem;
  }
}