:root {
  --bg: #0f1419;
  --surface: #1a2332;
  --border: #2d3a4d;
  --text: #e7ecf3;
  --muted: #8b9cb3;
  --accent: #5b8def;
  --danger: #e85d5d;
  --ok: #3ecf8e;
  --warn: #e6b84d;
  --safe-top: env(safe-area-inset-top, 0px);
  --safe-right: env(safe-area-inset-right, 0px);
  --safe-bottom: env(safe-area-inset-bottom, 0px);
  --safe-left: env(safe-area-inset-left, 0px);
  font-family: system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
}

* {
  box-sizing: border-box;
}

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

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  line-height: 1.5;
  min-height: 100vh;
  min-height: 100dvh;
  padding:
    var(--safe-top)
    var(--safe-right)
    var(--safe-bottom)
    var(--safe-left);
  -webkit-tap-highlight-color: transparent;
}

.site-header {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.5rem 1rem;
  padding: 0.75rem max(1.25rem, var(--safe-left)) 0.75rem max(1.25rem, var(--safe-right));
  padding-top: max(0.75rem, var(--safe-top));
  border-bottom: 1px solid var(--border);
  background: var(--surface);
}

.site-header a {
  color: var(--text);
  text-decoration: none;
}

.site-header nav {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.35rem 0.75rem;
}

.site-header nav a {
  color: var(--muted);
  padding: 0.35rem 0.5rem;
  min-height: 44px;
  display: inline-flex;
  align-items: center;
}

.site-header nav a:hover,
.site-header nav a:focus-visible {
  color: var(--text);
}

.logo {
  font-weight: 600;
  min-height: 44px;
  display: inline-flex;
  align-items: center;
}

.container {
  max-width: 720px;
  margin: 0 auto;
  width: 100%;
  padding: 1.25rem max(1rem, var(--safe-left)) 2rem max(1rem, var(--safe-right));
  padding-bottom: max(2rem, var(--safe-bottom));
}

h1 {
  font-size: clamp(1.35rem, 4vw, 1.5rem);
  margin: 0 0 1rem;
}

h2 {
  font-size: 1.1rem;
  margin: 1.5rem 0 0.75rem;
}

a {
  color: var(--accent);
}

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

.stack {
  display: flex;
  flex-direction: column;
  gap: 0.75rem;
}

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

.card-list li {
  padding: 0.65rem 0;
  border-bottom: 1px solid var(--border);
}

label {
  display: block;
  font-size: 0.85rem;
  color: var(--muted);
  margin-bottom: 0.25rem;
}

input[type="text"],
input[type="email"],
input[type="password"],
input[type="file"],
textarea {
  width: 100%;
  max-width: 100%;
  padding: 0.65rem 0.75rem;
  border: 1px solid var(--border);
  border-radius: 8px;
  background: var(--bg);
  color: var(--text);
  font-size: 16px;
}

textarea {
  min-height: 5rem;
  resize: vertical;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.65rem 1rem;
  min-height: 44px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text);
  cursor: pointer;
  font-size: 1rem;
  text-decoration: none;
  touch-action: manipulation;
}

.btn:hover {
  border-color: var(--muted);
}

.btn:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

.btn-primary {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
}

.btn-primary:hover {
  filter: brightness(1.08);
}

.btn-danger {
  border-color: var(--danger);
  color: var(--danger);
  background: transparent;
}

.btn-small {
  padding: 0.4rem 0.65rem;
  min-height: 40px;
  font-size: 0.875rem;
}

.row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  align-items: center;
}

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

.flashcard {
  perspective: 1000px;
  margin: 1rem 0 1.5rem;
  touch-action: manipulation;
}

.flashcard-inner {
  position: relative;
  min-height: min(50vh, 280px);
  transition: transform 0.35s ease;
  transform-style: preserve-3d;
  cursor: pointer;
  border-radius: 12px;
}

.flashcard.is-flipped .flashcard-inner {
  transform: rotateY(180deg);
}

.flashcard-face {
  position: absolute;
  inset: 0;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  border-radius: 12px;
  border: 1px solid var(--border);
  background: var(--surface);
  padding: clamp(1rem, 4vw, 1.25rem);
  display: flex;
  flex-direction: column;
  justify-content: center;
  overflow: auto;
  -webkit-overflow-scrolling: touch;
}

.flashcard-back {
  transform: rotateY(180deg);
}

.flashcard-face img {
  max-width: 100%;
  max-height: min(40vh, 200px);
  object-fit: contain;
  margin-top: 0.5rem;
  border-radius: 6px;
}

.review-actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.65rem;
  margin-top: 1rem;
}

.review-actions .btn {
  flex: 1 1 auto;
  min-width: min(100%, 140px);
}

.review-actions .btn-wrong {
  border-color: var(--danger);
  color: var(--danger);
}

.review-actions .btn-almost {
  border-color: var(--warn);
  color: var(--warn);
}

.review-actions .btn-right {
  border-color: var(--ok);
  color: var(--ok);
}

@media (max-width: 520px) {
  .review-actions {
    flex-direction: column;
  }

  .review-actions .btn {
    width: 100%;
    min-width: 0;
  }
}

.inline-form {
  display: inline;
}

.hint {
  font-size: 0.85rem;
  color: var(--muted);
  margin-top: 0.5rem;
}