/* Shared two-sided staircase layout */

.lesson-stairs {
  list-style: none;
  margin: 0 auto;
  padding: 0.25rem 0 0;
  width: min(100%, 1040px);
  position: relative;
  z-index: 1;
}

.lesson-stairs::before {
  content: "";
  position: absolute;
  left: 50%;
  top: 0.5rem;
  bottom: 0.5rem;
  width: 2px;
  transform: translateX(-50%);
  background: var(--border);
  pointer-events: none;
}

.lesson-stairs--asc::before {
  background: linear-gradient(180deg, transparent 0%, var(--accent) 45%, transparent 100%);
}

.lesson-stairs--te::before {
  background: linear-gradient(180deg, transparent 0%, var(--te-accent) 45%, transparent 100%);
}

.lesson-stairs .lesson-step {
  margin: 0;
  padding: 0 0 1.25rem;
  display: grid;
  grid-template-columns: minmax(0, 1fr) 4.5rem minmax(0, 1fr);
  gap: 0 1.5rem;
  align-items: start;
}

.lesson-stairs .lesson-step:last-child {
  padding-bottom: 0;
}

.lesson-step-node {
  grid-column: 2;
  grid-row: 1;
  display: flex;
  justify-content: center;
  padding-top: 1.25rem;
  position: relative;
  z-index: 2;
}

.lesson-step-num {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 2.75rem;
  height: 2.75rem;
  font-family: var(--font-display);
  font-size: 1rem;
  font-weight: 800;
  line-height: 1;
  border-radius: 50%;
  animation: none;
  box-shadow: none;
}

.lesson-stairs--asc .lesson-step-num {
  color: var(--accent);
  background: var(--accent-dim);
  border: 1px solid rgba(66, 185, 131, 0.4);
}

.lesson-stairs--te .lesson-step-num {
  color: var(--te-accent);
  background: var(--te-dim);
  border: 1px solid rgba(91, 141, 239, 0.4);
}

.lesson-stairs--asc .lesson-step--module .lesson-step-num {
  color: var(--text-muted);
  background: rgba(139, 156, 179, 0.12);
  border-color: var(--border);
}

a.lesson-step-card {
  text-decoration: none;
  color: inherit;
}

.lesson-stairs .lesson-step-card {
  position: relative;
  width: 100%;
  max-width: 420px;
  padding: 1.15rem 1.3rem;
  background: var(--bg-elevated);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-card);
  transition: border-color 0.2s, box-shadow 0.2s, transform 0.2s;
  clip-path: none;
}

.lesson-stairs .lesson-step-card::before {
  content: "";
  position: absolute;
  top: 0;
  left: 0;
  bottom: 0;
  width: 3px;
  background: var(--accent);
  border-radius: var(--radius) 0 0 var(--radius);
  opacity: 1;
}

.lesson-stairs--te .lesson-step-card::before {
  background: var(--te-accent);
}

.lesson-stairs .lesson-step:nth-child(odd) .lesson-step-card {
  grid-column: 1;
  justify-self: end;
}

.lesson-stairs .lesson-step:nth-child(even) .lesson-step-card {
  grid-column: 3;
  justify-self: start;
}

.lesson-stairs .lesson-step:nth-child(even) .lesson-step-card::before {
  left: auto;
  right: 0;
  border-radius: 0 var(--radius) var(--radius) 0;
}

.lesson-stairs .lesson-step-card::after {
  display: none;
}

.lesson-stairs .lesson-step-card:hover {
  border-color: rgba(66, 185, 131, 0.4);
  box-shadow: var(--shadow-card-hover);
  transform: translateY(-2px);
}

.lesson-stairs--te .lesson-step-card:hover {
  border-color: rgba(91, 141, 239, 0.5);
}

.lesson-stairs .lesson-step--soon .lesson-step-card,
.lesson-stairs .lesson-step--module .lesson-step-card {
  border-style: dashed;
  opacity: 0.92;
}

.lesson-stairs .lesson-step--soon .lesson-step-card:hover,
.lesson-stairs .lesson-step--module .lesson-step-card:hover {
  transform: none;
}

.lesson-step-title {
  text-shadow: none;
}

.lesson-stairs--asc .lesson-step-link {
  color: var(--accent);
  background: var(--accent-dim);
  border: 1px solid rgba(66, 185, 131, 0.35);
  border-radius: 8px;
  text-transform: none;
  letter-spacing: 0;
  box-shadow: none;
}

.lesson-stairs--te .lesson-step-link {
  color: var(--te-accent);
  background: var(--te-dim);
  border: 1px solid rgba(91, 141, 239, 0.35);
  border-radius: 8px;
  text-transform: none;
  box-shadow: none;
}

.lesson-stairs--asc .lesson-step-link:hover {
  color: #0a0f14;
  background: var(--accent);
  border-color: var(--accent);
  box-shadow: none;
}

.lesson-stairs--te .lesson-step-link:hover {
  color: #fff;
  background: var(--te-accent);
  border-color: var(--te-accent);
  box-shadow: none;
}

.lesson-stairs--asc .lesson-step:nth-child(even) .lesson-step-link:hover {
  background: var(--accent);
  border-color: var(--accent);
}

.lesson-step-desc--strong {
  font-family: var(--font-display);
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--text);
}

.lesson-step-card--accent {
  border-color: rgba(66, 185, 131, 0.35);
  background: linear-gradient(135deg, var(--accent-dim) 0%, var(--bg-elevated) 100%);
}

@media (max-width: 960px) {
  .lesson-stairs::before {
    left: 1.375rem;
    transform: none;
  }

  .lesson-stairs .lesson-step {
    grid-template-columns: 3.25rem 1fr;
    gap: 0 1rem;
  }

  .lesson-step-node {
    grid-column: 1;
    padding-top: 1rem;
  }

  .lesson-stairs .lesson-step-card,
  .lesson-stairs .lesson-step:nth-child(odd) .lesson-step-card,
  .lesson-stairs .lesson-step:nth-child(even) .lesson-step-card {
    grid-column: 2;
    justify-self: stretch;
    max-width: none;
  }
}