/* ========================================
   About - History (연혁) 3-Column Timeline
   ======================================== */

.about-history {
  background-color: var(--color-white);
  padding: var(--space-4xl) 0;
}

.about-history__inner {
  display: flex;
  flex-direction: column;
  position: relative;
}

/* Vertical line (base gray) */
.about-history__line {
  display: none;
}

/* Era Block */
.about-history__era {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-2xl);
  padding-bottom: var(--space-4xl);
}

.about-history__era:last-child {
  padding-bottom: 0;
}

/* Era Header (Left Column) */
.about-history__era-header {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.about-history__era-range {
  font-size: 2.25rem;
  font-weight: 800;
  color: var(--color-text-dark);
  letter-spacing: -0.04em;
  line-height: 1.2;
}

.about-history__era-desc {
  font-size: 1rem;
  font-weight: 400;
  color: var(--color-text-dark);
  letter-spacing: -0.02em;
  line-height: 1.6;
}

/* Era Dot (Center Column) - hidden on mobile */
.about-history__era-dot {
  display: none;
}

/* Era Timeline (Right Column) */
.about-history__era-timeline {
  display: flex;
  flex-direction: column;
  gap: var(--space-3xl);
}

/* Year Block */
.about-history__year-block {
  display: flex;
  flex-direction: column;
  gap: var(--space-md);
}

.about-history__year {
  font-size: 1.5rem;
  font-weight: 700;
  color: var(--color-text-dark);
  letter-spacing: -0.04em;
  line-height: 1.3;
}

/* Events */
.about-history__events {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.about-history__event {
  display: flex;
  gap: 0.75rem;
  align-items: flex-start;
}

.about-history__event-month {
  font-size: 1.1875rem;
  font-weight: 500;
  color: var(--color-text-dark);
  letter-spacing: -0.02em;
  line-height: 1.7;
  min-width: 1.75rem;
  flex-shrink: 0;
}

.about-history__event-text {
  font-size: 1.1875rem;
  font-weight: 400;
  color: var(--color-text-dark);
  letter-spacing: -0.02em;
  line-height: 1.7;
}

/* Tablet */
@media (min-width: 768px) {
  .about-history {
    padding: var(--space-5xl) 0;
  }

  .about-history__era {
    grid-template-columns: 0.75fr 40px 1fr;
    gap: 0 var(--space-xl);
    padding-bottom: var(--space-5xl);
  }

  .about-history__era-range {
    font-size: 2.75rem;
  }

  .about-history__era-desc {
    font-size: 1.0625rem;
  }

  /* Vertical lines - positioned via JS */
  .about-history__line {
    display: block;
    position: absolute;
    top: 0;
    bottom: 0;
    width: 2px;
    pointer-events: none;
  }

  .about-history__line--base {
    background-color: var(--color-border);
  }

  .about-history__line--progress {
    background-color: var(--color-primary);
    bottom: auto;
    height: 0;
    transition: height 0.05s linear;
  }

  /* Center dot */
  .about-history__era-dot {
    display: flex;
    justify-content: center;
    padding-top: 0.75rem;
    position: relative;
    z-index: 2;
  }

  .about-history__era-dot::before {
    content: "";
    width: 0.875rem;
    height: 0.875rem;
    border-radius: 50%;
    border: 2px solid var(--color-border);
    background-color: var(--color-white);
    flex-shrink: 0;
    transition: border-color 0.3s ease, background-color 0.3s ease;
  }

  .about-history__era-dot.is-passed::before {
    border-color: var(--color-primary);
    background-color: var(--color-primary);
  }

  .about-history__year {
    font-size: 1.625rem;
  }

  .about-history__event-month {
    font-size: 1.125rem;
    min-width: 2rem;
  }

  .about-history__event-text {
    font-size: 1.125rem;
  }
}

/* Desktop */
@media (min-width: 1024px) {
  .about-history {
    padding: var(--space-section) 0;
  }

  .about-history__era {
    grid-template-columns: 0.75fr 50px 1fr;
    gap: 0 var(--space-2xl);
  }

  .about-history__era-range {
    font-size: 3.25rem;
  }

  .about-history__era-desc {
    font-size: 1.25rem;
  }

  .about-history__year {
    font-size: 1.75rem;
  }

  .about-history__event-month,
  .about-history__event-text {
    font-size: 1.1875rem;
  }
}