/* =========================================================
   THEORY — страница теории
   ========================================================= */

.theory {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: 100px 24px 80px;
}

/* Hero */
.theory-hero {
  text-align: center;
  padding: 40px 0 32px;
}
.theory-hero-inner {
  max-width: 720px;
  margin: 0 auto;
}
.theory-title {
  font-family: var(--f-serif);
  font-size: clamp(36px, 5vw, 64px);
  font-weight: 600;
  line-height: 1.1;
  color: var(--c-ink);
  margin-bottom: 12px;
}
.theory-sub {
  font-size: clamp(15px, 1.3vw, 18px);
  color: var(--c-ink-soft);
  line-height: 1.6;
}

/* Filters */
.theory-filters {
  display: flex;
  justify-content: center;
  padding: 0 0 32px;
}
.theory-filters-inner {
  display: flex;
  gap: 8px;
  flex-wrap: wrap;
  justify-content: center;
}
.filter-btn {
  padding: 10px 18px;
  border-radius: 100px;
  background: transparent;
  border: 1px solid var(--c-line-strong);
  font-family: var(--f-sans);
  font-size: 13px;
  font-weight: 500;
  color: var(--c-ink-soft);
  cursor: pointer;
  transition: all var(--t-fast);
}
.filter-btn:hover {
  background: rgba(44, 24, 16, 0.05);
  color: var(--c-ink);
  border-color: var(--c-ink);
}
.filter-btn.active {
  background: var(--c-ink);
  color: var(--c-paper);
  border-color: var(--c-ink);
}

/* Grid */
.theory-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: var(--gap-lg);
}

/* Card */
.theory-card {
  background: var(--c-paper);
  border: 1px solid var(--c-line);
  border-radius: var(--r-md);
  padding: 24px;
  display: flex;
  flex-direction: column;
  gap: 14px;
  transition: transform var(--t-med), box-shadow var(--t-med), border-color var(--t-med);
  cursor: pointer;
}
.theory-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--sh-card);
  border-color: var(--c-accent);
}

.theory-card-tag {
  align-self: flex-start;
  font-size: 11px;
  letter-spacing: 2px;
  text-transform: uppercase;
  color: var(--c-accent);
  padding: 4px 10px;
  border: 1px solid var(--c-accent);
  border-radius: 100px;
}

.theory-card-title {
  font-family: var(--f-sans);
  font-size: 20px;
  font-weight: 700;
  color: var(--c-ink);
  line-height: 1.25;
}

.theory-card-text {
  font-size: 14px;
  color: var(--c-ink-soft);
  line-height: 1.55;
  flex: 1;
}

.theory-card-meta {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding-top: 14px;
  border-top: 1px solid var(--c-line);
  font-size: 12px;
  color: var(--c-ink-muted);
  font-family: var(--f-mono);
  letter-spacing: 0.5px;
}

.theory-card-meta i {
  color: var(--c-accent);
  margin-right: 6px;
}

/* Empty */
.theory-empty {
  text-align: center;
  padding: 60px 24px;
  color: var(--c-ink-muted);
  font-size: 15px;
}
.theory-empty[hidden] { display: none; }

/* Responsive */
@media (max-width: 900px) {
  .theory-grid {
    grid-template-columns: repeat(2, 1fr);
  }
}
@media (max-width: 600px) {
  .theory {
    padding: 90px 16px 60px;
  }
  .theory-grid {
    grid-template-columns: 1fr;
  }
  .filter-btn {
    padding: 8px 14px;
    font-size: 12px;
  }
}