/* ==========================================================================
   交互部件的样式：算式面板、步进器、折叠块、手算挑战、小测验。
   （与神经网络课里的同名文件同源，去掉了矩阵相关的部分。）
   ========================================================================== */

/* ---------- 算式面板 ---------- */
.calc {
  margin-top: 14px;
  padding: 12px 16px;
  border-radius: var(--radius-sm);
  background: var(--surface-2);
  border: 1px solid var(--border);
  border-left: 4px solid var(--brand);
  font-family: var(--font-mono);
  font-size: 14px;
  line-height: 1.9;
  min-height: 78px;
  overflow-x: auto;
}
.calc.is-grad {
  border-left-color: var(--grad);
}
.calc .calc-title {
  font-family: var(--font-sans);
  font-size: 13px;
  font-weight: 700;
  color: var(--text-2);
  margin-bottom: 2px;
  display: flex;
  flex-wrap: wrap;
  gap: 4px 10px;
  align-items: center;
}
.calc .calc-title .hint {
  font-weight: 500;
  color: var(--muted);
}
.calc .calc-line {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 2px 6px;
}
.calc .term {
  display: inline-flex;
  align-items: center;
  padding: 0 7px;
  border-radius: 7px;
  background: var(--surface);
  border: 1px solid var(--border);
  white-space: nowrap;
  animation: termIn 0.35s ease both;
}
.calc .term .times {
  color: var(--muted);
  margin: 0 3px;
}
.calc .op {
  color: var(--muted);
}
.calc .res {
  font-weight: 800;
  color: var(--brand-ink);
  background: var(--brand-soft);
  padding: 0 9px;
  border-radius: 7px;
}
.calc.is-grad .res {
  color: var(--grad);
  background: var(--grad-soft);
}
.calc .sub {
  color: var(--muted);
  font-size: 12.5px;
}
.calc .pos {
  color: var(--c-pos-ink, #2563eb);
}
@keyframes termIn {
  from {
    opacity: 0;
    transform: translateY(4px);
  }
  to {
    opacity: 1;
    transform: none;
  }
}
.calc-hint {
  margin-top: 8px;
  font-size: 13px;
  color: var(--muted);
  display: flex;
  align-items: center;
  gap: 6px;
}
.calc-hint svg {
  width: 15px;
  height: 15px;
}

/* ---------- 步进器 ---------- */
.stepper {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  box-shadow: var(--shadow-1);
  overflow: hidden;
}
.stepper:focus-visible {
  outline: 2px solid var(--brand);
  outline-offset: 2px;
}
.stepmap {
  display: flex;
  align-items: stretch;
  gap: 0;
  padding: 14px 16px 12px;
  overflow-x: auto;
  background: linear-gradient(180deg, var(--surface-2), var(--surface));
  border-bottom: 1px solid var(--border);
  scrollbar-width: thin;
}
.stepmap-node {
  appearance: none;
  border: 0;
  background: transparent;
  cursor: pointer;
  padding: 0 4px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 6px;
  min-width: 62px;
  position: relative;
  color: var(--muted);
  font-size: 12px;
  font-weight: 600;
}
.stepmap-node::before {
  content: '';
  position: absolute;
  top: 13px;
  right: 50%;
  width: 100%;
  height: 3px;
  background: var(--border-strong);
  z-index: 0;
}
.stepmap-node:first-child::before {
  display: none;
}
.stepmap-node.done::before,
.stepmap-node.active::before {
  background: var(--tone-c, var(--brand));
}
.stepmap-dot {
  width: 28px;
  height: 28px;
  border-radius: 50%;
  display: grid;
  place-items: center;
  font-size: 12px;
  font-weight: 800;
  background: var(--surface);
  border: 2px solid var(--border-strong);
  z-index: 1;
  color: var(--muted);
  transition: all 0.2s;
}
.stepmap-node.done .stepmap-dot {
  background: var(--tone-c, var(--brand));
  border-color: var(--tone-c, var(--brand));
  color: #fff;
}
.stepmap-node.active .stepmap-dot {
  background: var(--surface);
  border-color: var(--tone-c, var(--brand));
  color: var(--tone-c, var(--brand));
  box-shadow: 0 0 0 5px color-mix(in srgb, var(--tone-c, var(--brand)) 20%, transparent);
  transform: scale(1.12);
}
.stepmap-node.active {
  color: var(--text);
}
.stepmap-node:hover .stepmap-dot {
  border-color: var(--tone-c, var(--brand));
}
.stepmap-label {
  white-space: nowrap;
}

.step-body {
  padding: 22px 26px 8px;
  animation: stepIn 0.35s ease both;
}
@keyframes stepIn {
  from {
    opacity: 0;
    transform: translateY(8px);
  }
  to {
    opacity: 1;
    transform: none;
  }
}
.step-title {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 6px 12px;
  margin-bottom: 14px;
}
.step-title .num {
  font-family: var(--font-mono);
  font-size: 13px;
  font-weight: 800;
  color: #fff;
  background: var(--tone-c, var(--brand));
  padding: 1px 10px;
  border-radius: 999px;
}
.step-title h3 {
  font-size: 22px;
}
.step-title .out-shape {
  margin-left: auto;
  font-size: 12.5px;
  color: var(--muted);
  font-family: var(--font-mono);
}
.step-cols {
  display: grid;
  grid-template-columns: minmax(0, 1.25fr) minmax(0, 1fr);
  gap: 8px 32px;
  align-items: start;
}
.step-cols p {
  margin-bottom: 0.7em;
}
.step-viz {
  margin: 18px 0 8px;
  padding: 18px 18px 14px;
  background: var(--surface);
  border: 1px dashed var(--border-strong);
  border-radius: var(--radius);
  overflow-x: auto;
}
.step-viz-hd {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 8px 14px;
  margin-bottom: 14px;
}
.step-nav {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 10px;
  padding: 14px 20px;
  border-top: 1px solid var(--border);
  background: var(--surface-2);
}
.step-nav .progress {
  font-size: 13px;
  color: var(--muted);
  font-family: var(--font-mono);
}
.step-nav .kbd-hint {
  font-size: 12.5px;
  color: var(--muted);
}

@media (max-width: 900px) {
  .step-cols {
    grid-template-columns: minmax(0, 1fr);
  }
  .step-body {
    padding: 18px 14px 6px;
  }
  .step-title h3 {
    font-size: 19px;
  }
  .step-viz {
    padding: 12px 10px;
  }
  .step-nav .kbd-hint {
    display: none;
  }
}


.stepmap {
  position: relative;
}

/* ---------- 算式面板里的小部件 ---------- */
.calc .lbl {
  font-family: var(--font-sans);
  font-weight: 700;
  font-size: 12.5px;
  color: var(--text-2);
  background: var(--surface-3);
  border-radius: 6px;
  padding: 0 8px;
  white-space: nowrap;
}
.calc .res.soft {
  font-weight: 700;
  font-size: 0.96em;
  padding: 0 7px;
}
.calc .calc-line + .calc-line {
  margin-top: 4px;
}
.calc .calc-line .sub {
  font-family: var(--font-sans);
}
.calc .term sup {
  font-size: 0.75em;
}
.calc > .sub {
  font-family: var(--font-sans);
  margin-top: 4px;
}

/* 算式面板 + 旁边的图 */
.split {
  display: grid;
  grid-template-columns: minmax(0, 1.55fr) minmax(0, 1fr);
  gap: 16px;
  align-items: stretch;
}
.split > .calc {
  min-width: 0;
}
@media (max-width: 900px) {
  .split {
    grid-template-columns: minmax(0, 1fr);
    gap: 0;
  }
}

/* ---------- 折叠块 ---------- */
.details {
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  background: var(--surface);
  margin: 14px 0;
}
.details > summary {
  cursor: pointer;
  padding: 10px 16px;
  font-weight: 700;
  color: var(--text-2);
  list-style: none;
  display: flex;
  align-items: center;
  gap: 8px;
  user-select: none;
}
.details > summary::-webkit-details-marker {
  display: none;
}
.details > summary::before {
  content: '';
  width: 7px;
  height: 7px;
  border-right: 2px solid var(--muted);
  border-bottom: 2px solid var(--muted);
  transform: rotate(-45deg);
  transition: transform 0.2s;
  flex: none;
}
.details[open] > summary::before {
  transform: rotate(45deg);
}
.details > summary:hover {
  color: var(--brand-ink);
}
.details-b {
  padding: 4px 18px 14px;
  border-top: 1px dashed var(--border);
}
.details-b > :last-child {
  margin-bottom: 0;
}

/* ---------- 手算挑战 ---------- */
.challenge {
  margin: 16px 0 6px;
  padding: 14px 16px;
  border-radius: var(--radius-sm);
  background: var(--accent-soft);
  border: 1px dashed color-mix(in srgb, var(--accent) 55%, transparent);
}
.challenge.is-ok {
  border-style: solid;
  border-color: var(--good);
  background: var(--good-soft);
}
.challenge-hd {
  display: flex;
  align-items: center;
  gap: 8px;
  color: var(--accent);
  margin-bottom: 4px;
}
.challenge-hd svg {
  width: 18px;
  height: 18px;
}
.challenge-q {
  margin-bottom: 10px;
  font-size: 15px;
}
.challenge-row {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  align-items: center;
}
.challenge-row input {
  width: 190px;
  max-width: 100%;
}
.challenge-fb {
  margin-top: 10px;
  font-size: 14px;
  line-height: 1.6;
}
.challenge-fb svg {
  width: 16px;
  height: 16px;
  vertical-align: -3px;
  margin-right: 4px;
}
.challenge-fb.ok {
  color: var(--good);
  font-weight: 700;
}
.challenge-fb.bad {
  color: var(--bad);
}
.challenge-fb.note {
  color: var(--text-2);
}
.challenge-reveal {
  margin-top: 6px;
  padding: 8px 12px;
  border-radius: 8px;
  background: var(--surface);
  color: var(--text);
  font-weight: 400;
  font-size: 13.5px;
  font-family: var(--font-mono);
  line-height: 1.8;
  overflow-x: auto;
}

/* ---------- 小测验 ---------- */
.quiz {
  display: grid;
  gap: 18px;
}
.quiz-hd {
  display: flex;
  align-items: center;
  gap: 10px;
  flex-wrap: wrap;
}
.quiz-hd b {
  font-size: 18px;
}
.quiz-q {
  display: flex;
  gap: 10px;
  font-weight: 700;
  margin-bottom: 8px;
}
.quiz-no {
  flex: none;
  width: 24px;
  height: 24px;
  border-radius: 50%;
  background: var(--brand);
  color: #fff;
  display: grid;
  place-items: center;
  font-size: 13px;
  margin-top: 2px;
}
.quiz-opts {
  display: grid;
  gap: 8px;
}
.quiz-opt {
  appearance: none;
  text-align: left;
  display: flex;
  gap: 10px;
  align-items: flex-start;
  padding: 9px 14px;
  border: 1px solid var(--border-strong);
  border-radius: 12px;
  background: var(--surface);
  cursor: pointer;
  font-size: 15px;
  line-height: 1.55;
  transition: border-color 0.15s, background 0.15s;
}
.quiz-opt:hover:not(:disabled) {
  border-color: var(--brand);
  background: var(--brand-soft);
}
.quiz-opt:disabled {
  cursor: default;
}
.quiz-key {
  flex: none;
  width: 22px;
  height: 22px;
  border-radius: 6px;
  background: var(--surface-3);
  display: grid;
  place-items: center;
  font-family: var(--font-mono);
  font-size: 12px;
  font-weight: 800;
}
.quiz-opt.is-right {
  border-color: var(--good);
  background: var(--good-soft);
}
.quiz-opt.is-wrong {
  border-color: var(--bad);
  background: var(--bad-soft);
}
.quiz-explain {
  margin-top: 8px;
  padding: 10px 14px;
  border-radius: 10px;
  font-size: 14.5px;
  line-height: 1.65;
}
.quiz-explain.ok {
  background: var(--good-soft);
}
.quiz-explain.bad {
  background: var(--warn-soft);
}