/* ===== Card-specific Variables ===== */
:root {
  --card-front-bg: #ffffff;
  --card-front-text: #1a1a2e;
  --card-back-bg: #1a1a2e;
  --card-back-text: #e8eaf6;
  --progress-bg: #d1dce5;
}

#dark-mode:checked ~ .site-wrapper {
  --card-front-bg: #21262d;
  --card-front-text: #e6edf3;
  --progress-bg: #21262d;
}

/* ===== Category Filter ===== */
#cat-html:checked     ~ .site-wrapper .card:not(.html-card)     { display: none; }
#cat-css:checked      ~ .site-wrapper .card:not(.css-card)      { display: none; }
#cat-boxmodel:checked ~ .site-wrapper .card:not(.boxmodel-card) { display: none; }

/* Active filter label highlight */
#cat-all:checked      ~ .site-wrapper label[for="cat-all"],
#cat-html:checked     ~ .site-wrapper label[for="cat-html"],
#cat-css:checked      ~ .site-wrapper label[for="cat-css"],
#cat-boxmodel:checked ~ .site-wrapper label[for="cat-boxmodel"] {
  background: var(--accent);
  color: #ffffff;
  border-color: var(--accent);
}

/* ===== Nav Filter Tabs ===== */
.filter-tabs {
  display: flex;
  gap: 0.4rem;
  flex: 1;
}

.filter-label {
  display: inline-flex;
  align-items: center;
  padding: 0.3rem 0.9rem;
  border-radius: 20px;
  border: 1.5px solid rgba(255, 255, 255, 0.2);
  color: var(--nav-text);
  font-size: 0.82rem;
  font-weight: 500;
  cursor: pointer;
  transition: background 0.2s, color 0.2s, border-color 0.2s;
  user-select: none;
  white-space: nowrap;
}

.filter-label:hover {
  background: rgba(255, 255, 255, 0.1);
  color: var(--nav-link-hover);
}

/* ===== Card Count Label ===== */
.progress-section {
  padding: 0.35rem 2rem;
  background: rgba(0, 0, 0, 0.12);
  display: flex;
  align-items: center;
  justify-content: flex-end;
}

.progress-text {
  font-size: 0.75rem;
  color: rgba(255, 255, 255, 0.45);
  white-space: nowrap;
}

/* ===== Content & Grid ===== */
.content {
  padding: 2.5rem 2rem;
  flex: 1;
}

.cards-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 1.5rem;
  max-width: 1200px;
  margin: 0 auto;
}

/* ===== Flip Card ===== */
.card-toggle { display: none; }

.card {
  perspective: 1000px;
  height: 280px;
  cursor: pointer;
}

.card-inner {
  position: relative;
  width: 100%;
  height: 100%;
  transform-style: preserve-3d;
  transition: transform 0.55s cubic-bezier(0.4, 0.2, 0.2, 1);
  border-radius: 16px;
  display: block;
}

.card-toggle:checked + .card-inner {
  transform: rotateY(180deg);
}

.card-front,
.card-back {
  position: absolute;
  inset: 0;
  border-radius: 16px;
  backface-visibility: hidden;
  -webkit-backface-visibility: hidden;
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  padding: 1.5rem;
  box-shadow: 0 4px 20px var(--shadow);
  transition: box-shadow 0.3s ease;
}

.card-inner:hover .card-front,
.card-inner:hover .card-back {
  box-shadow: 0 8px 32px var(--shadow-hover);
}

.card-front {
  background: var(--card-front-bg);
  border: 1.5px solid var(--border);
  color: var(--card-front-text);
}

.card-back {
  background: var(--card-back-bg);
  border: 1.5px solid rgba(255, 255, 255, 0.08);
  color: var(--card-back-text);
  transform: rotateY(180deg);
  overflow-y: auto;
}

/* ===== Code blocks inside card answers ===== */
.answer pre {
  white-space: pre-wrap;
  word-break: break-word;
  background: rgba(255, 255, 255, 0.07);
  border-radius: 6px;
  padding: 0.4em 0.7em;
  font-family: 'Fira Code', 'Courier New', monospace;
  font-size: 0.78em;
  line-height: 1.45;
  width: 100%;
  margin: 0.25em 0;
  overflow-x: auto;
  flex-shrink: 0;
}

/* ===== Tags ===== */
.tag {
  display: inline-flex;
  align-items: center;
  padding: 0.2rem 0.65rem;
  border-radius: 6px;
  font-size: 0.72rem;
  font-weight: 700;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  width: fit-content;
}

.tag-html     { background: rgba(67, 97, 238, 0.12); color: var(--tag-html); }
.tag-css      { background: rgba(123, 45, 139, 0.12); color: var(--tag-css); }
.tag-boxmodel { background: rgba(26, 127, 75, 0.12); color: var(--tag-boxmodel); }

.card-back .tag-html     { background: rgba(67, 97, 238, 0.3); color: #a5b4fc; }
.card-back .tag-css      { background: rgba(167, 139, 250, 0.3); color: #c4b5fd; }
.card-back .tag-boxmodel { background: rgba(52, 211, 153, 0.3); color: #6ee7b7; }

/* ===== Card Text ===== */
.question {
  font-size: 1.05rem;
  font-weight: 600;
  line-height: 1.5;
  flex: 1;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  align-content: center;
}

.answer {
  font-size: 0.9rem;
  font-weight: 400;
  line-height: 1.65;
  flex: 1;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  align-content: center;
}

/* <br> 태그를 flex 컨텍스트에서 줄바꿈으로 동작하게 처리 */
.question br,
.answer br {
  width: 100%;
  height: 0;
}

.answer strong {
  color: #4cc9f0;
  font-weight: 700;
}

.answer code {
  background: rgba(255, 255, 255, 0.1);
  padding: 0.1em 0.35em;
  border-radius: 4px;
  font-family: 'Fira Code', 'Courier New', monospace;
  font-size: 0.85em;
}

.card-hint {
  font-size: 0.7rem;
  color: var(--text-secondary);
  text-align: right;
}

.card-back .card-hint {
  color: rgba(255, 255, 255, 0.35);
}

/* ===== Responsive ===== */
@media (max-width: 640px) {
  .filter-tabs {
    flex-wrap: wrap;
  }

  .content {
    padding: 1.5rem 1rem;
  }

  .cards-grid {
    grid-template-columns: 1fr;
  }
}