/* SED vertical loop — row-aligned spine + full-width steps */
.sed-loop {
  --sed-accent: #176b52;
  --sed-glow: rgba(23, 107, 82, 0.22);
  --sed-rail: 84px;
  position: relative;
  margin: 28px 0 12px;
  border: 1px solid var(--line);
  border-radius: 14px;
  overflow: hidden;
  background: #fff;
  box-shadow: 0 8px 30px rgba(23, 26, 24, 0.06);
}

.sed-loop__fiber {
  position: absolute;
  left: 0;
  top: 0;
  bottom: 0;
  width: calc(var(--sed-rail) + 36px);
  z-index: 0;
  overflow: hidden;
  pointer-events: none;
  opacity: 0.72;
  -webkit-mask-image:
    linear-gradient(to right, rgba(0, 0, 0, 1) 0%, rgba(0, 0, 0, 1) 55%, rgba(0, 0, 0, 0.35) 72%, transparent 100%),
    linear-gradient(to bottom, rgba(0, 0, 0, 1) 0%, rgba(0, 0, 0, 1) 76%, rgba(0, 0, 0, 0.4) 88%, transparent 100%);
  -webkit-mask-composite: source-in;
  mask-image:
    linear-gradient(to right, rgba(0, 0, 0, 1) 0%, rgba(0, 0, 0, 1) 55%, rgba(0, 0, 0, 0.35) 72%, transparent 100%),
    linear-gradient(to bottom, rgba(0, 0, 0, 1) 0%, rgba(0, 0, 0, 1) 76%, rgba(0, 0, 0, 0.4) 88%, transparent 100%);
  mask-composite: intersect;
}

.sed-loop__inner {
  position: relative;
  z-index: 1;
  display: flex;
  flex-direction: column;
  min-height: 440px;
}

.sed-loop__spine {
  position: absolute;
  left: 0;
  top: 0;
  width: var(--sed-rail);
  height: 100%;
  z-index: 1;
  pointer-events: none;
  overflow: visible;
}

.sed-loop__track {
  stroke: #dde4e0;
  stroke-width: 2;
  fill: none;
}

.sed-loop__progress-fill {
  stroke: var(--sed-accent);
  stroke-width: 2.5;
  fill: none;
  stroke-linecap: round;
  opacity: 0.4;
}

.sed-loop__flow {
  stroke: url(#sed-flow-grad);
  stroke-width: 2.5;
  fill: none;
  stroke-linecap: round;
  filter: drop-shadow(0 0 3px var(--sed-glow));
}

.sed-loop__packet {
  fill: #fff;
  stroke: var(--sed-accent);
  stroke-width: 2;
  filter: drop-shadow(0 0 5px var(--sed-glow));
}

.sed-loop__rows {
  position: relative;
  z-index: 2;
  flex: 1;
  display: grid;
  grid-template-columns: var(--sed-rail) 1fr;
  grid-template-rows: repeat(4, 1fr);
  gap: 0;
  min-height: 400px;
  padding: 10px 0 6px;
  background: transparent;
  pointer-events: none;
}

.sed-loop__row {
  display: contents;
}

.sed-loop__node {
  position: relative;
  z-index: 3;
  justify-self: center;
  align-self: center;
  width: 36px;
  height: 36px;
  padding: 0;
  border: none;
  background: transparent;
  cursor: pointer;
  outline: none;
  margin-top: 0;
  pointer-events: auto;
}

.sed-loop__card {
  width: 100%;
  align-self: center;
  padding: 12px 18px 12px 10px;
  border-radius: 10px;
  cursor: pointer;
  border: 1px solid transparent;
  background: transparent;
  box-sizing: border-box;
  pointer-events: auto;
  transition:
    opacity 0.35s ease,
    background 0.4s ease,
    border-color 0.4s ease,
    box-shadow 0.4s ease;
}

.sed-loop__node:focus-visible .sed-loop__chip {
  outline: 2px solid var(--sed-accent);
  outline-offset: 2px;
}

.sed-loop__chip {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  border-radius: 9px;
  border: 1.5px solid #c8d2cd;
  background: #fff;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 11px;
  font-weight: 700;
  color: #7a8480;
  transition: background 0.4s ease, border-color 0.4s ease, color 0.35s ease, box-shadow 0.4s ease;
}

.sed-loop__node.is-done .sed-loop__chip {
  background: #e8f2ed;
  border-color: var(--sed-accent);
  color: var(--sed-accent);
}

.sed-loop__node.is-active .sed-loop__chip {
  background: var(--sed-accent);
  border-color: var(--sed-accent);
  color: #fff;
  box-shadow: 0 0 14px var(--sed-glow);
}

.sed-loop__ripple {
  position: absolute;
  inset: -4px;
  border-radius: 12px;
  border: 1px solid var(--sed-accent);
  opacity: 0;
  pointer-events: none;
}

.sed-loop__node.is-active .sed-loop__ripple {
  animation: sed-ripple 2.2s ease-out infinite;
}

.sed-loop__node.is-active .sed-loop__ripple--2 {
  animation-delay: 0.55s;
}

@keyframes sed-ripple {
  0% { opacity: 0.5; transform: scale(0.92); }
  100% { opacity: 0; transform: scale(1.35); }
}

.sed-loop__card:not(.is-active) {
  opacity: 0.78;
}

.sed-loop__card.is-active {
  opacity: 1;
  background: linear-gradient(135deg, rgba(238, 248, 244, 0.95) 0%, rgba(255, 255, 255, 0.98) 100%);
  border-color: rgba(223, 228, 225, 0.9);
  box-shadow: 0 2px 16px rgba(23, 26, 24, 0.05);
}

.sed-loop[data-step="learn"] .sed-loop__card.is-active {
  box-shadow: 0 2px 20px rgba(23, 107, 82, 0.09);
}

.sed-loop__card-head {
  display: flex;
  align-items: baseline;
  gap: 10px;
  flex-wrap: wrap;
}

.sed-loop__card-num {
  font-family: Georgia, "Times New Roman", serif;
  font-size: 1.05rem;
  font-weight: 700;
  color: var(--sed-accent);
  flex-shrink: 0;
}

.sed-loop__card h3 {
  margin: 0;
  font-size: 1rem;
  line-height: 1.35;
  display: inline;
}

.sed-loop__card-tag {
  font-size: 0.66rem;
  font-weight: 600;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin-left: 6px;
}

.sed-loop__card p {
  margin: 6px 0 0;
  font-size: 0.88rem;
  line-height: 1.48;
  color: #4a5350;
}

.sed-loop__card:not(.is-active) p {
  color: #5f6864;
}

.sed-loop__card p > span {
  display: block;
}

.sed-loop__hint {
  position: relative;
  z-index: 1;
  margin: 0;
  padding: 0 16px 10px;
  font-size: 0.72rem;
  color: var(--muted);
  text-align: right;
  background: linear-gradient(to bottom, rgba(255, 255, 255, 0.55) 0%, #fff 55%);
}

.sed-loop.is-reduced .sed-loop__fiber,
.sed-loop.is-reduced .sed-loop__spine,
.sed-loop.is-reduced .sed-loop__flow,
.sed-loop.is-reduced .sed-loop__packet,
.sed-loop.is-reduced .sed-loop__ripple {
  display: none;
}

.sed-loop.is-reduced .sed-loop__rows {
  display: block;
  min-height: auto;
  padding: 12px 14px;
}

.sed-loop.is-reduced .sed-loop__row {
  display: block;
  margin-bottom: 8px;
}

.sed-loop.is-reduced .sed-loop__node {
  display: none;
}

.sed-loop.is-reduced .sed-loop__card {
  opacity: 1;
  cursor: default;
  border-color: var(--line);
  background: #fff;
}

.sed-loop.is-reduced .sed-loop__card p {
  margin-top: 6px;
}

@media (max-width: 720px) {
  .sed-loop__inner,
  .sed-loop__rows {
    min-height: auto;
  }

  .sed-loop__fiber {
    width: 100%;
    height: 120px;
    bottom: auto;
    opacity: 0.72;
    -webkit-mask-image: linear-gradient(to bottom, rgba(0, 0, 0, 1) 0%, rgba(0, 0, 0, 0.4) 70%, transparent 100%);
    mask-image: linear-gradient(to bottom, rgba(0, 0, 0, 1) 0%, rgba(0, 0, 0, 0.4) 70%, transparent 100%);
  }

  .sed-loop__spine {
    display: none;
  }

  .sed-loop__rows {
    grid-template-columns: 1fr;
    padding: 10px 12px 8px;
  }

  .sed-loop__row {
    display: block;
  }

  .sed-loop__node {
    display: none;
  }

  .sed-loop__card:not(.is-active) {
    opacity: 0.78;
  }
}

@media (prefers-reduced-motion: reduce) {
  .sed-loop__node.is-active .sed-loop__ripple {
    animation: none;
  }
}