#concept-first-guide {
  --cfg-ink: #15202b;
  --cfg-muted: #52606d;
  --cfg-line: #cbd5df;
  --cfg-soft: #f4f7f9;
  --cfg-blue: #176b87;
  --cfg-blue-soft: #e6f4f7;
  --cfg-green: #1f7650;
  --cfg-green-soft: #e8f5ee;
  --cfg-red: #a53f3f;
  --cfg-red-soft: #faecec;
  margin: 2rem 0;
  padding: 1.5rem;
  border: 1px solid var(--cfg-line);
  border-left: 4px solid var(--cfg-blue);
  border-radius: 6px;
  background: #fff;
  color: var(--cfg-ink);
}

#concept-first-guide *,
#concept-first-guide *::before,
#concept-first-guide *::after {
  box-sizing: border-box;
}

.cfg-kicker {
  margin: 0 0 0.45rem;
  color: var(--cfg-blue);
  font-size: 0.76rem;
  font-weight: 750;
  letter-spacing: 0;
  text-transform: uppercase;
}

#concept-first-guide h2 {
  margin: 0;
  color: var(--cfg-ink);
  font-size: clamp(1.25rem, 2.2vw, 1.65rem);
  line-height: 1.25;
  letter-spacing: 0;
}

.cfg-mechanism {
  max-width: 72ch;
  margin: 0.7rem 0 1.25rem;
  color: var(--cfg-muted);
  line-height: 1.65;
}

.cfg-flow {
  display: grid;
  grid-template-columns: minmax(0, 1fr) auto minmax(0, 1fr) auto minmax(0, 1fr) auto minmax(0, 1fr);
  align-items: stretch;
  gap: 0.45rem;
  margin-bottom: 1.25rem;
}

.cfg-flow span:not(.cfg-arrow) {
  display: grid;
  place-items: center;
  min-height: 3.4rem;
  padding: 0.65rem;
  border: 1px solid var(--cfg-line);
  border-radius: 4px;
  background: var(--cfg-soft);
  color: var(--cfg-ink);
  font-size: 0.84rem;
  font-weight: 700;
  line-height: 1.25;
  text-align: center;
}

.cfg-arrow {
  align-self: center;
  color: var(--cfg-blue);
  font-size: 1rem;
  font-weight: 800;
}

.cfg-stepper {
  min-height: 15rem;
  padding: 1.15rem;
  border: 1px solid var(--cfg-line);
  border-radius: 5px;
  background: var(--cfg-soft);
}

.cfg-step {
  display: none;
}

.cfg-step.is-active {
  display: block;
  animation: cfg-reveal 160ms ease-out;
}

.cfg-step-label {
  margin: 0 0 0.35rem;
  color: var(--cfg-blue);
  font-size: 0.78rem;
  font-weight: 750;
}

.cfg-step h3 {
  margin: 0;
  color: var(--cfg-ink);
  font-size: 1.1rem;
  letter-spacing: 0;
}

.cfg-step p {
  margin: 0.65rem 0;
  color: var(--cfg-muted);
  line-height: 1.6;
}

.cfg-evidence {
  margin-top: 0.9rem;
  padding: 0.85rem 1rem;
  border-left: 3px solid var(--cfg-blue);
  background: #fff;
  color: var(--cfg-ink);
  font-family: ui-monospace, SFMono-Regular, Consolas, "Liberation Mono", monospace;
  font-size: 0.86rem;
  line-height: 1.5;
  overflow-wrap: anywhere;
}

.cfg-evidence span,
.cfg-evidence code {
  display: block;
}

.cfg-evidence span {
  margin-bottom: 0.35rem;
  color: var(--cfg-blue);
  font-family: inherit;
  font-size: 0.75rem;
  font-weight: 750;
  text-transform: uppercase;
}

.cfg-evidence code {
  color: var(--cfg-ink);
  font: inherit;
  white-space: normal;
}

.cfg-controls {
  display: flex;
  justify-content: space-between;
  gap: 0.75rem;
  margin-top: 1rem;
}

#concept-first-guide button {
  min-height: 2.55rem;
  padding: 0.55rem 0.9rem;
  border: 1px solid var(--cfg-blue);
  border-radius: 4px;
  background: #fff;
  color: var(--cfg-blue);
  font: inherit;
  font-size: 0.9rem;
  font-weight: 700;
  line-height: 1.25;
  cursor: pointer;
  white-space: normal;
}

#concept-first-guide button:hover:not(:disabled) {
  background: var(--cfg-blue-soft);
}

#concept-first-guide button:focus-visible {
  outline: 3px solid color-mix(in srgb, var(--cfg-blue) 35%, transparent);
  outline-offset: 2px;
}

#concept-first-guide button:disabled {
  border-color: var(--cfg-line);
  color: #8795a1;
  cursor: not-allowed;
}

.cfg-checkpoint {
  margin-top: 1.25rem;
  padding-top: 1.15rem;
  border-top: 1px solid var(--cfg-line);
}

.cfg-checkpoint p {
  margin: 0 0 0.8rem;
  line-height: 1.55;
}

.cfg-checkpoint button {
  display: block;
  width: 100%;
  margin-top: 0.55rem;
  text-align: left;
}

.cfg-checkpoint button.is-correct {
  border-color: var(--cfg-green);
  background: var(--cfg-green-soft);
  color: var(--cfg-green);
}

.cfg-checkpoint button.is-wrong {
  border-color: var(--cfg-red);
  background: var(--cfg-red-soft);
  color: var(--cfg-red);
}

#cfg-feedback {
  min-height: 2.8rem;
  margin-top: 0.75rem;
  padding: 0.7rem 0.85rem;
  border-radius: 4px;
  background: var(--cfg-soft);
  color: var(--cfg-muted);
  line-height: 1.45;
}

.cfg-takeaway {
  margin-top: 1.25rem;
  padding: 1rem;
  border: 1px solid var(--cfg-line);
  border-radius: 5px;
  background: var(--cfg-blue-soft);
}

.cfg-takeaway strong {
  color: var(--cfg-blue);
}

.cfg-takeaway p {
  margin: 0.35rem 0 0;
  color: var(--cfg-ink);
  line-height: 1.55;
}

@keyframes cfg-reveal {
  from {
    opacity: 0;
    transform: translateY(3px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

@media (prefers-reduced-motion: reduce) {
  .cfg-step.is-active {
    animation: none;
  }
}

@media (max-width: 760px) {
  #concept-first-guide {
    margin: 1.4rem 0;
    padding: 1rem;
  }

  .cfg-flow {
    grid-template-columns: minmax(0, 1fr);
  }

  .cfg-arrow {
    justify-self: center;
    transform: rotate(90deg);
  }

  .cfg-stepper {
    min-height: 17rem;
    padding: 1rem;
  }

  .cfg-controls {
    align-items: stretch;
  }

  .cfg-controls button {
    flex: 1 1 0;
  }
}

@media (prefers-color-scheme: dark) {
  #concept-first-guide {
    --cfg-ink: #e6edf3;
    --cfg-muted: #a9b5c1;
    --cfg-line: #465563;
    --cfg-soft: #17212a;
    --cfg-blue: #69bdd2;
    --cfg-blue-soft: #16343d;
    --cfg-green: #78c99f;
    --cfg-green-soft: #17372a;
    --cfg-red: #e49595;
    --cfg-red-soft: #3d2023;
    background: #101820;
  }

  .cfg-evidence,
  #concept-first-guide button {
    background: #101820;
  }
}