/**
 * research.css
 * ─────────────────────────────────────────────────────────────
 * PURPOSE: Styles for "Research Notebook" — blogs, AI concepts,
 *          learning logs, and notes presented as notebook pages.
 *
 * LOGIC: Cards styled like handwritten notebook entries with
 *        a yellow ruled-line aesthetic mixed with the dark/light
 *        theme. Category filter tabs hide/show cards via JS.
 *        Search input filters cards in real-time via JS.
 *
 * CUSTOMIZATION: Add new notebook entries in index.html.
 *                Adjust categories in the filter tabs.
 * ─────────────────────────────────────────────────────────────
 */

#research { background: var(--color-bg); }

/* ── SEARCH & FILTER ROW ───────────────────────────────────── */
.research__controls {
  display: flex;
  gap: var(--space-4);
  align-items: center;
  margin-bottom: var(--space-8);
  flex-wrap: wrap;
}

/* Search input */
.research__search-wrap {
  position: relative;
  flex: 1;
  min-width: 200px;
}

.research__search-icon {
  position: absolute;
  left: var(--space-4);
  top: 50%;
  transform: translateY(-50%);
  color: var(--color-text-faint);
  font-size: 16px;
  pointer-events: none;
}

.research__search {
  width: 100%;
  padding: var(--space-3) var(--space-4) var(--space-3) var(--space-10);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  font-size: var(--text-sm);
  color: var(--color-text);
  transition: all var(--transition-fast);
  outline: none;
}

.research__search::placeholder { color: var(--color-text-faint); }

.research__search:focus {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(139, 92, 246, 0.1);
}

/* Filter chips */
.research__filters {
  display: flex;
  gap: var(--space-2);
  flex-wrap: wrap;
}

.research__filter {
  padding: var(--space-2) var(--space-4);
  border-radius: var(--radius-full);
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: var(--weight-medium);
  color: var(--color-text-muted);
  border: 1px solid var(--color-border);
  cursor: pointer;
  transition: all var(--transition-fast);
  background: transparent;
  letter-spacing: 0.05em;
}

.research__filter:hover {
  color: var(--color-primary);
  border-color: var(--color-primary);
}

.research__filter.active {
  color: white;
  background: var(--color-primary);
  border-color: var(--color-primary);
}

/* ── NOTEBOOK GRID ─────────────────────────────────────────── */
.research__grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: var(--space-5);
}

/* ── NOTEBOOK CARD ─────────────────────────────────────────── */
.notebook-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  overflow: hidden;
  transition: all var(--transition-base);
  display: flex;
  flex-direction: column;
  position: relative;
}

/* Left accent stripe (category color) */
.notebook-card::before {
  content: '';
  position: absolute;
  left: 0; top: 0; bottom: 0;
  width: 4px;
  background: var(--card-accent, var(--color-primary));
  border-radius: var(--radius-sm) 0 0 var(--radius-sm);
}

.notebook-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-card);
  border-color: rgba(139, 92, 246, 0.35);
}

/* Notebook card header */
.notebook-card__header {
  padding: var(--space-5) var(--space-5) 0 calc(var(--space-5) + 4px);
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: var(--space-2);
}

.notebook-card__category {
  font-family: var(--font-mono);
  font-size: 10px;
  font-weight: var(--weight-bold);
  color: var(--card-accent, var(--color-primary));
  text-transform: uppercase;
  letter-spacing: 0.15em;
  background: rgba(139, 92, 246, 0.08);
  padding: 2px var(--space-2);
  border-radius: var(--radius-sm);
}

.notebook-card__date {
  font-family: var(--font-mono);
  font-size: 10px;
  color: var(--color-text-faint);
}

/* Card body */
.notebook-card__body {
  padding: var(--space-3) var(--space-5) var(--space-5) calc(var(--space-5) + 4px);
  flex: 1;
  display: flex;
  flex-direction: column;
}

.notebook-card__title {
  font-size: var(--text-base);
  font-weight: var(--weight-bold);
  color: var(--color-text);
  line-height: 1.35;
  margin-bottom: var(--space-3);
}

.notebook-card__excerpt {
  font-size: var(--text-sm);
  color: var(--color-text-muted);
  line-height: 1.65;
  display: -webkit-box;
  -webkit-line-clamp: 3;
  -webkit-box-orient: vertical;
  overflow: hidden;
  flex: 1;
  margin-bottom: var(--space-4);
}

/* Tags */
.notebook-card__tags {
  display: flex;
  flex-wrap: wrap;
  gap: var(--space-2);
}

.notebook-tag {
  font-family: var(--font-mono);
  font-size: 10px;
  color: var(--color-text-faint);
  background: rgba(139, 92, 246, 0.06);
  padding: 1px var(--space-2);
  border-radius: var(--radius-sm);
  border: 1px solid var(--color-border);
}

/* Read more link */
.notebook-card__read-more {
  display: flex;
  align-items: center;
  gap: var(--space-1);
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
  color: var(--color-primary);
  margin-top: var(--space-4);
  transition: gap var(--transition-fast);
}

.notebook-card:hover .notebook-card__read-more {
  gap: var(--space-2);
}

/* ── CURRENTLY LEARNING CHECKLIST ─────────────────────────── */
.currently-learning {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-2xl);
  padding: var(--space-7);
  margin-top: var(--space-10);
}

.currently-learning__title {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  color: var(--color-primary);
  letter-spacing: 0.15em;
  text-transform: uppercase;
  margin-bottom: var(--space-5);
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.learning-list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: var(--space-4);
}

.learning-item {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  padding: var(--space-4);
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-xl);
  transition: all var(--transition-base);
}

.learning-item:hover {
  border-color: rgba(139, 92, 246, 0.4);
  transform: translateY(-2px);
}

.learning-item__icon {
  font-size: 24px;
  flex-shrink: 0;
}

.learning-item__info { flex: 1; }

.learning-item__name {
  font-weight: var(--weight-semibold);
  font-size: var(--text-sm);
  color: var(--color-text);
  margin-bottom: var(--space-1);
}

.learning-item__progress-wrap {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.learning-item__bar {
  flex: 1;
  height: 4px;
  background: rgba(139, 92, 246, 0.1);
  border-radius: var(--radius-full);
  overflow: hidden;
}

.learning-item__fill {
  height: 100%;
  background: var(--gradient-primary);
  border-radius: var(--radius-full);
  width: 0%;
  transition: width 1.2s ease;
}

.learning-item__pct {
  font-family: var(--font-mono);
  font-size: 10px;
  color: var(--color-primary);
  white-space: nowrap;
}

/* "No results" state */
.research__no-results {
  text-align: center;
  padding: var(--space-12);
  color: var(--color-text-faint);
  font-family: var(--font-mono);
  font-size: var(--text-sm);
  display: none;
}

.research__no-results.visible { display: block; }