:root {
  --color-bg: #f5f5f0;
  --color-surface: #ffffff;
  --color-text: #1c1c1a;
  --color-muted: #6b6b64;
  --color-primary: #1d4d3f;
  --color-primary-contrast: #ffffff;
  --color-secondary: #e4e4dc;
  --color-secondary-text: #1c1c1a;
  --color-border: #ddddd2;
  --color-error-bg: #fbe4e1;
  --color-error-text: #8c2a1d;
  --color-success-bg: #e2f0e1;
  --color-success-text: #1d4d2c;
  --radius: 12px;
  --space-1: 4px;
  --space-2: 8px;
  --space-3: 16px;
  --space-4: 24px;
  color-scheme: light dark;
}

@media (prefers-color-scheme: dark) {
  :root {
    --color-bg: #14140f;
    --color-surface: #201f1a;
    --color-text: #ece9e0;
    --color-muted: #a3a196;
    --color-primary: #4caf82;
    --color-primary-contrast: #0b1f16;
    --color-secondary: #2a2a22;
    --color-secondary-text: #ece9e0;
    --color-border: #3a392f;
    --color-error-bg: #402420;
    --color-error-text: #f2b4a9;
    --color-success-bg: #1f3626;
    --color-success-text: #b9e6bf;
  }
}

* {
  box-sizing: border-box;
}

html {
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  background: var(--color-bg);
  color: var(--color-text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  font-size: 17px;
  line-height: 1.5;
  padding-bottom: env(safe-area-inset-bottom);
}

a {
  color: var(--color-primary);
  text-decoration: none;
}

.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--space-3) var(--space-3);
  padding-top: calc(var(--space-3) + env(safe-area-inset-top));
  background: var(--color-primary);
  color: var(--color-primary-contrast);
  position: sticky;
  top: 0;
  z-index: 10;
}

.brand {
  color: var(--color-primary-contrast);
  font-weight: 700;
  font-size: 1.2rem;
}

.nav-toggle {
  background: none;
  border: none;
  color: var(--color-primary-contrast);
  font-size: 1.5rem;
  padding: var(--space-1) var(--space-2);
  cursor: pointer;
  display: none;
}

.app-nav {
  display: flex;
  gap: var(--space-2);
  flex-wrap: wrap;
  padding: var(--space-2) var(--space-3);
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 9;
}

.app-nav a {
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius);
  color: var(--color-text);
  font-size: 0.95rem;
}

.app-nav a.active {
  background: var(--color-primary);
  color: var(--color-primary-contrast);
}

.app-main {
  max-width: 720px;
  margin: 0 auto;
  padding: var(--space-3) var(--space-3) calc(var(--space-4) * 2);
}

h1 {
  font-size: 1.6rem;
  margin: var(--space-2) 0 var(--space-3);
}

h2 {
  font-size: 1.2rem;
  margin: 0 0 var(--space-2);
}

.card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: var(--space-3);
  margin-bottom: var(--space-3);
}

.auth-card {
  max-width: 400px;
  margin: var(--space-4) auto;
}

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

.list {
  list-style: none;
  margin: 0;
  padding: 0;
}

.list li {
  padding: var(--space-2) 0;
  border-bottom: 1px solid var(--color-border);
}

.list li:last-child {
  border-bottom: none;
}

.subject-tag {
  display: inline-block;
  background: var(--color-secondary);
  color: var(--color-secondary-text);
  border-radius: 999px;
  padding: 2px 10px;
  font-size: 0.8rem;
  font-weight: 600;
  margin-right: var(--space-2);
}

form {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

label {
  font-weight: 600;
  font-size: 0.9rem;
  margin-top: var(--space-2);
}

input, select, textarea {
  font-size: 1rem;
  padding: var(--space-2);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  background: var(--color-bg);
  color: var(--color-text);
  width: 100%;
}

textarea {
  resize: vertical;
}

.btn {
  display: inline-block;
  border: none;
  border-radius: var(--radius);
  padding: var(--space-2) var(--space-3);
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  text-align: center;
  margin-top: var(--space-2);
}

.btn-primary {
  background: var(--color-primary);
  color: var(--color-primary-contrast);
}

.btn-secondary {
  background: var(--color-secondary);
  color: var(--color-secondary-text);
}

.alert {
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius);
  margin-bottom: var(--space-3);
}

.alert-error {
  background: var(--color-error-bg);
  color: var(--color-error-text);
}

.alert-success {
  background: var(--color-success-bg);
  color: var(--color-success-text);
}

.steps {
  display: flex;
  flex-direction: column;
  gap: var(--space-2);
}

details.step summary {
  cursor: pointer;
  font-weight: 600;
  list-style: none;
}

details.step summary::-webkit-details-marker {
  display: none;
}

.step-index {
  color: var(--color-muted);
  margin-right: var(--space-1);
}

.step-body {
  margin-top: var(--space-3);
}

.badge {
  display: inline-block;
  font-size: 0.75rem;
  border-radius: 999px;
  padding: 2px 8px;
  margin-left: var(--space-2);
}

.badge-done {
  background: var(--color-success-bg);
  color: var(--color-success-text);
}

.step-done {
  opacity: 0.75;
}

.qa-list {
  list-style: none;
  padding: 0;
  margin: 0;
}

.qa-item {
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: var(--space-2);
  margin-bottom: var(--space-2);
}

.qa-item summary {
  cursor: pointer;
  font-weight: 500;
}

.qa-answer {
  margin-top: var(--space-2);
  color: var(--color-muted);
}

.filter-bar {
  display: flex;
  gap: var(--space-2);
  margin-bottom: var(--space-3);
}

.filter-bar a {
  padding: var(--space-1) var(--space-3);
  border-radius: 999px;
  border: 1px solid var(--color-border);
  color: var(--color-text);
}

.filter-bar a.active {
  background: var(--color-primary);
  color: var(--color-primary-contrast);
  border-color: var(--color-primary);
}

.hw-list li {
  border: none;
  padding: 0;
}

.hw-item {
  display: flex;
  align-items: flex-start;
  gap: var(--space-3);
  padding: var(--space-2) 0;
  border-bottom: 1px solid var(--color-border);
}

.hw-toggle-form {
  margin: 0;
}

.hw-check {
  width: 32px;
  height: 32px;
  min-width: 32px;
  border-radius: 50%;
  border: 2px solid var(--color-primary);
  background: var(--color-surface);
  color: var(--color-primary);
  font-weight: 700;
  cursor: pointer;
}

.hw-done .hw-check {
  background: var(--color-primary);
  color: var(--color-primary-contrast);
}

.hw-done .hw-text {
  text-decoration: line-through;
  color: var(--color-muted);
}

.exam-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  flex-wrap: wrap;
}

.exam-item form {
  margin: 0;
}

.card.error {
  border: 1px solid #b3261e;
  background: #fceceb;
  color: #7a1a15;
}

.plan-text {
  white-space: pre-wrap;
  font-family: inherit;
  font-size: 0.95rem;
  line-height: 1.5;
}

@media (max-width: 600px) {
  .nav-toggle {
    display: inline-block;
  }
  .app-nav {
    display: none;
    flex-direction: column;
  }
  .app-nav.open {
    display: flex;
  }
  .exam-item {
    flex-direction: column;
    align-items: flex-start;
  }
}