/* =====================================================
   PHYSICSVERSE — LOVE FOR PHYSICS
   Class 11 · Chapter 1 · Units and Measurements
   ===================================================== */

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/* ── FEEL IT ── */
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/* ── LEARN IT ── */
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/* ── SEE IT — Simulations ── */
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/* Cosmic Scale Explorer */
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}
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.scale-labels {
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}

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  min-height: 130px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  transition: all 0.3s;
}
.obj-emoji { font-size: 2.5rem; margin-bottom: 0.5rem; line-height: 1; }
.obj-name {
  font-weight: 700;
  font-size: 1.05rem;
  color: var(--text);
  margin-bottom: 0.25rem;
}
.obj-size {
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}
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}
.obj-order {
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  padding: 0.2rem 0.65rem;
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  border-radius: 100px;
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}

/* Unit Converter */
.converter-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.75rem;
  margin-top: 1rem;
}
@media (max-width: 540px) { .converter-grid { grid-template-columns: 1fr; } }

.conv-field label {
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  font-weight: 600;
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  text-transform: uppercase;
  margin-bottom: 0.4rem;
}

.conv-select, .conv-input {
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  background: rgba(0,0,0,0.35);
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  border-radius: var(--r);
  color: var(--text);
  font-family: 'Inter', sans-serif;
  font-size: 0.95rem;
  outline: none;
  transition: border-color 0.2s;
  -webkit-appearance: none;
}
.conv-select:focus, .conv-input:focus { border-color: var(--cyan); }
.conv-select option { background: #0d1230; }

.conv-arrow {
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  font-size: 1.3rem;
  color: var(--cyan);
  padding-top: 1.4rem;
}
@media (max-width: 540px) { .conv-arrow { padding-top: 0; padding-bottom: 0.5rem; transform: rotate(90deg); } }

.conv-result {
  background: rgba(0,0,0,0.4);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 1rem 1.25rem;
  margin-top: 1rem;
  font-family: 'JetBrains Mono', monospace;
  font-size: clamp(1rem, 3vw, 1.3rem);
  color: var(--green);
  text-align: center;
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  align-items: center;
  justify-content: center;
}

.conv-step {
  margin-top: 0.6rem;
  font-size: 0.8rem;
  color: var(--text-muted);
  text-align: center;
  font-style: italic;
}

/* Sig Fig Detective */
.sigfig-display {
  background: rgba(0,0,0,0.4);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 1.5rem;
  text-align: center;
  margin-bottom: 1.25rem;
}
.sigfig-number {
  font-family: 'JetBrains Mono', monospace;
  font-size: clamp(2rem, 7vw, 3rem);
  color: var(--amber);
  letter-spacing: 0.05em;
  line-height: 1;
}
.sigfig-prompt {
  font-size: 0.85rem;
  color: var(--text-dim);
  margin-top: 0.4rem;
}

.sigfig-options {
  display: flex;
  gap: 0.6rem;
  justify-content: center;
  flex-wrap: wrap;
  margin-bottom: 1rem;
}
.sigfig-btn {
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  height: 3rem;
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  border: 2px solid var(--border);
  background: var(--bg-card);
  color: var(--text);
  font-family: 'JetBrains Mono', monospace;
  font-size: 1.1rem;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.2s;
}
.sigfig-btn:hover { border-color: var(--cyan); color: var(--cyan); background: var(--cyan-dim); }
.sigfig-btn.correct { background: var(--green-dim); border-color: var(--green); color: var(--green); }
.sigfig-btn.wrong { background: var(--red-dim); border-color: var(--red); color: var(--red); }

.sigfig-feedback {
  min-height: 2.5rem;
  text-align: center;
  font-size: 0.9rem;
  padding: 0.5rem;
  border-radius: var(--r);
  transition: all 0.3s;
}
.sigfig-feedback.correct { background: var(--green-dim); color: var(--green); }
.sigfig-feedback.wrong { background: var(--red-dim); color: var(--red); }

.sigfig-progress {
  display: flex;
  gap: 0.4rem;
  justify-content: center;
  margin-bottom: 1rem;
}
.progress-dot {
  width: 10px; height: 10px;
  border-radius: 50%;
  background: rgba(255,255,255,0.1);
  border: 1px solid rgba(255,255,255,0.15);
  transition: all 0.3s;
}
.progress-dot.done-correct { background: var(--green); border-color: var(--green); }
.progress-dot.done-wrong { background: var(--red); border-color: var(--red); }

.sigfig-score-row {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 0.75rem;
  font-size: 0.85rem;
  color: var(--text-dim);
}
.sigfig-score-num {
  font-family: 'JetBrains Mono', monospace;
  color: var(--cyan);
  font-size: 0.95rem;
}

/* ── SOLVE IT ── */
.problem-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--r-lg);
  margin-bottom: 1.25rem;
  overflow: hidden;
}

.problem-header {
  padding: 1.15rem 1.4rem;
  display: flex;
  align-items: center;
  gap: 0.9rem;
  cursor: pointer;
  transition: background 0.2s;
  user-select: none;
}
.problem-header:hover { background: var(--bg-card-hover); }

.problem-num {
  width: 2.4rem;
  height: 2.4rem;
  min-width: 2.4rem;
  background: var(--cyan-dim);
  border: 1px solid var(--border);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: 'Bebas Neue', sans-serif;
  font-size: 1.1rem;
  color: var(--cyan);
}

.problem-title { flex: 1; font-weight: 600; font-size: 0.97rem; }
.problem-toggle { color: var(--text-muted); font-size: 1.1rem; transition: transform 0.3s; }
.problem-toggle.open { transform: rotate(180deg); }

.problem-body { display: none; padding: 0 1.4rem 1.4rem; }
.problem-body.open { display: block; }

.problem-q {
  padding: 0.9rem 1.1rem;
  background: rgba(255,255,255,0.025);
  border-radius: var(--r);
  margin-bottom: 1rem;
  font-size: 0.97rem;
  line-height: 1.7;
  border-left: 3px solid var(--amber);
}

.solution-label {
  font-size: 0.7rem;
  font-weight: 700;
  letter-spacing: 0.12em;
  color: var(--green);
  text-transform: uppercase;
  margin-bottom: 0.75rem;
}

.step {
  display: flex;
  gap: 0.85rem;
  margin-bottom: 0.7rem;
  align-items: flex-start;
}

.step-n {
  width: 1.5rem;
  height: 1.5rem;
  min-width: 1.5rem;
  background: var(--green-dim);
  border: 1px solid var(--border-green);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.7rem;
  font-weight: 700;
  color: var(--green);
  margin-top: 0.2rem;
  line-height: 1.5rem;
  text-align: center;
}

.step-c { flex: 1; font-size: 0.93rem; line-height: 1.7; }

.final-ans {
  background: var(--green-dim);
  border: 1px solid var(--border-green);
  border-radius: var(--r);
  padding: 0.75rem 1rem;
  margin-top: 0.5rem;
  font-weight: 600;
  color: var(--green);
  font-size: 0.95rem;
}

/* ── TEST IT — MCQ Quiz ── */
.quiz-status {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.75rem 1.25rem;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--r);
  margin-bottom: 1.5rem;
  font-size: 0.85rem;
}
.quiz-score-display {
  font-family: 'JetBrains Mono', monospace;
  color: var(--cyan);
}
.quiz-progress-text { color: var(--text-muted); }

.mcq-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--r-lg);
  padding: 1.4rem;
  margin-bottom: 1.1rem;
  transition: border-color 0.35s;
}
.mcq-card.c-state { border-color: var(--green); }
.mcq-card.w-state { border-color: var(--red); }

.mcq-q {
  font-weight: 600;
  font-size: 0.97rem;
  margin-bottom: 1rem;
  line-height: 1.65;
}
.mcq-qnum {
  font-family: 'JetBrains Mono', monospace;
  color: var(--cyan);
  margin-right: 0.4rem;
  font-size: 0.82rem;
}

.mcq-options { display: flex; flex-direction: column; gap: 0.45rem; }

.mcq-opt {
  display: flex;
  align-items: flex-start;
  gap: 0.7rem;
  padding: 0.65rem 0.9rem;
  background: rgba(255,255,255,0.03);
  border: 1px solid rgba(255,255,255,0.07);
  border-radius: var(--r);
  cursor: pointer;
  transition: all 0.18s;
  text-align: left;
  width: 100%;
  font-family: 'Inter', sans-serif;
  font-size: 0.92rem;
  color: var(--text);
}
.mcq-opt:hover:not(:disabled) {
  background: rgba(0,217,255,0.07);
  border-color: var(--border);
}
.mcq-opt:disabled { cursor: default; }
.mcq-opt.s-correct { background: var(--green-dim); border-color: var(--green); color: var(--green); }
.mcq-opt.s-wrong { background: var(--red-dim); border-color: var(--red); color: var(--red); }
.mcq-opt.reveal-correct { background: var(--green-dim); border-color: var(--green); }

.opt-lbl {
  font-family: 'JetBrains Mono', monospace;
  font-weight: 700;
  color: var(--text-muted);
  min-width: 1.1rem;
  font-size: 0.8rem;
}

.mcq-exp {
  display: none;
  margin-top: 0.65rem;
  padding: 0.65rem 0.9rem;
  background: rgba(0,217,255,0.05);
  border: 1px solid var(--border);
  border-radius: var(--r);
  font-size: 0.86rem;
  color: var(--text-dim);
  line-height: 1.65;
}
.mcq-exp.show { display: block; }

.quiz-footer {
  display: flex;
  justify-content: center;
  gap: 1rem;
  margin-top: 1.5rem;
  flex-wrap: wrap;
}

.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.7rem 1.6rem;
  border: none;
  border-radius: 100px;
  font-family: 'Inter', sans-serif;
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
}
.btn-primary { background: var(--cyan); color: #0a0e27; }
.btn-primary:hover { background: #22e5ff; transform: translateY(-1px); box-shadow: 0 8px 24px rgba(0,217,255,0.3); }
.btn-secondary { background: transparent; color: var(--cyan); border: 1.5px solid var(--cyan); }
.btn-secondary:hover { background: var(--cyan-dim); }
.btn-amber { background: var(--amber); color: #0a0e27; }
.btn-amber:hover { background: #ffc966; transform: translateY(-1px); }

.quiz-result-box {
  display: none;
  text-align: center;
  padding: 2.5rem 1.5rem;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--r-lg);
  margin-top: 1.5rem;
}
.quiz-result-box.show { display: block; }

.result-big {
  font-family: 'Bebas Neue', 'Oswald', sans-serif;
  font-size: clamp(4rem, 12vw, 6rem);
  color: var(--cyan);
  line-height: 1;
  text-shadow: 0 0 40px rgba(0,217,255,0.4);
}
.result-label { font-size: 0.85rem; color: var(--text-dim); margin-top: 0.25rem; }
.result-msg { font-size: 1.05rem; color: var(--text); margin-top: 1rem; font-weight: 500; }

/* ── Footer ── */
.site-footer {
  padding: 2.5rem 1.5rem;
  text-align: center;
  border-top: 1px solid var(--border);
  background: rgba(0,0,0,0.3);
}
.footer-text {
  font-family: 'Bebas Neue', 'Oswald', sans-serif;
  font-size: clamp(0.85rem, 2.5vw, 1.1rem);
  color: var(--text-dim);
  letter-spacing: 0.07em;
  line-height: 1.7;
}
.footer-accent { color: var(--cyan); }

/* ── Utilities ── */
p { margin-bottom: 0.75rem; }
p:last-child { margin-bottom: 0; }
strong { color: var(--amber); font-weight: 600; }
em { color: var(--text-dim); font-style: italic; }
.divider { width: 50px; height: 3px; background: linear-gradient(90deg, var(--cyan), transparent); border-radius: 2px; margin: 1.25rem 0; }

.katex-display { overflow-x: auto; padding: 0.5rem 0; }

::-webkit-scrollbar { width: 6px; height: 6px; }
::-webkit-scrollbar-track { background: var(--bg); }
::-webkit-scrollbar-thumb { background: rgba(0,217,255,0.2); border-radius: 3px; }

@media (max-width: 600px) {
  .section { padding: 2.5rem 0 4rem; }
  .section-header { padding-bottom: 1.75rem; }
  .card, .sim-card { padding: 1.2rem; }
  .mcq-card { padding: 1.1rem; }
  .problem-header { padding: 1rem 1.1rem; }
  .problem-body { padding: 0 1.1rem 1.1rem; }
}

/* ══════════════════════════════════════
   LANGUAGE TOGGLE
══════════════════════════════════════ */
.lang-toggle {
  display: flex;
  gap: 0.35rem;
  margin-top: 0.9rem;
  justify-content: center;
  flex-wrap: wrap;
}

.lang-btn {
  min-width: 44px;
  min-height: 44px;
  padding: 0.3rem 0.75rem;
  border-radius: 100px;
  border: 1.5px solid var(--border);
  background: transparent;
  color: var(--text-dim);
  font-family: 'Inter', sans-serif;
  font-size: 0.82rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
  display: flex;
  align-items: center;
  justify-content: center;
  letter-spacing: 0.03em;
}
.lang-btn:hover { border-color: var(--cyan); color: var(--cyan); }
.lang-btn.active {
  background: var(--cyan);
  border-color: var(--cyan);
  color: #0a0e27;
}

/* ══════════════════════════════════════
   SECTION 2.21 — INSTRUMENTS
══════════════════════════════════════ */
.instrument-intro {
  background: var(--amber-dim);
  border: 1px solid var(--border-amber);
  border-left: 4px solid var(--amber);
  border-radius: var(--r);
  padding: 1.1rem 1.4rem;
  margin-bottom: 1.5rem;
  font-size: 0.95rem;
}

.parts-list {
  list-style: none;
  padding: 0;
  margin: 0.75rem 0;
}
.parts-list li {
  padding: 0.4rem 0 0.4rem 1.5rem;
  position: relative;
  border-bottom: 1px solid rgba(255,255,255,0.04);
  font-size: 0.93rem;
}
.parts-list li::before {
  content: '▸';
  position: absolute;
  left: 0;
  color: var(--cyan);
  font-size: 0.75rem;
  top: 0.5rem;
}

.step-method {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 1rem 1.25rem;
  margin-bottom: 0.75rem;
}
.step-method-num {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 1.6rem;
  height: 1.6rem;
  background: var(--cyan-dim);
  border: 1px solid var(--border);
  border-radius: 50%;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--cyan);
  margin-right: 0.6rem;
  vertical-align: middle;
}

.zero-error-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0.75rem;
  margin: 1rem 0;
}
@media (max-width: 560px) { .zero-error-grid { grid-template-columns: 1fr; } }

.ze-box {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 0.9rem 1.1rem;
}
.ze-box h4 { font-size: 0.85rem; font-weight: 700; margin-bottom: 0.4rem; }
.ze-box.positive h4 { color: var(--amber); }
.ze-box.negative h4 { color: var(--cyan); }

/* ══════════════════════════════════════
   SIMULATION 4 — VERNIER & SCREW GAUGE
══════════════════════════════════════ */
.vsg-tabs {
  display: flex;
  gap: 0.5rem;
  margin-bottom: 1.25rem;
  border-bottom: 1px solid var(--border);
  padding-bottom: 0.75rem;
  flex-wrap: wrap;
}
.vsg-tab {
  padding: 0.45rem 1.1rem;
  border-radius: 100px;
  border: 1.5px solid var(--border);
  background: transparent;
  color: var(--text-dim);
  font-family: 'Inter', sans-serif;
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
  min-height: 44px;
}
.vsg-tab:hover { border-color: var(--cyan); color: var(--cyan); }
.vsg-tab.active { background: var(--cyan); border-color: var(--cyan); color: #0a0e27; }

.vsg-canvas-wrap {
  background: rgba(0,0,0,0.4);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 1rem;
  margin-bottom: 1rem;
  overflow-x: auto;
  text-align: center;
}
.vsg-canvas-wrap canvas {
  max-width: 100%;
  height: auto;
}

.vsg-controls {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 0.6rem 1rem;
  align-items: center;
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 1rem 1.25rem;
  margin-bottom: 1rem;
  font-size: 0.88rem;
}
.vsg-controls label { color: var(--text-dim); white-space: nowrap; }
.vsg-controls input[type=range] {
  width: 100%;
  height: 6px;
  accent-color: var(--cyan);
  cursor: pointer;
}
@media (max-width: 480px) { .vsg-controls { grid-template-columns: 1fr; } }

.vsg-reading {
  background: rgba(0,0,0,0.35);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 1rem 1.25rem;
  margin-bottom: 1rem;
  font-family: 'JetBrains Mono', monospace;
  font-size: 0.88rem;
  line-height: 2;
}
.vsg-reading > div { color: var(--text-dim); }
.vsg-total {
  font-size: 1.05rem !important;
  color: var(--green) !important;
  font-weight: 700;
  padding-top: 0.5rem;
  border-top: 1px solid var(--border);
  margin-top: 0.4rem;
}

.vsg-practice {
  margin-top: 0.75rem;
  padding-top: 1rem;
  border-top: 1px solid var(--border);
}
.vsg-practice-title {
  font-size: 0.75rem;
  font-weight: 700;
  color: var(--text-muted);
  text-transform: uppercase;
  letter-spacing: 0.1em;
  margin-bottom: 0.75rem;
}
.vsg-new-btn {
  padding: 0.5rem 1.2rem;
  border-radius: 100px;
  border: 1.5px solid var(--amber);
  background: var(--amber-dim);
  color: var(--amber);
  font-family: 'Inter', sans-serif;
  font-size: 0.85rem;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
  min-height: 44px;
}
.vsg-new-btn:hover { background: var(--amber); color: #0a0e27; }

.vsg-practice-q {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 0.85rem 1.1rem;
  margin: 0.75rem 0;
  font-size: 0.9rem;
  line-height: 1.7;
}
.vsg-q-label {
  display: block;
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--cyan);
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 0.3rem;
}
.vsg-answer-input {
  padding: 0.6rem 1rem;
  border: 1.5px solid var(--border);
  border-radius: var(--r);
  background: rgba(0,0,0,0.3);
  color: var(--text);
  font-family: 'JetBrains Mono', monospace;
  font-size: 1rem;
  width: 140px;
  outline: none;
  transition: border-color 0.2s;
  margin-right: 0.5rem;
}
.vsg-answer-input:focus { border-color: var(--cyan); }
.vsg-check-btn {
  padding: 0.55rem 1.1rem;
  border-radius: var(--r);
  border: none;
  background: var(--cyan);
  color: #0a0e27;
  font-family: 'Inter', sans-serif;
  font-size: 0.88rem;
  font-weight: 700;
  cursor: pointer;
  transition: all 0.2s;
  min-height: 44px;
}
.vsg-check-btn:hover { background: #22e5ff; }

.vsg-practice-feedback {
  margin-top: 0.6rem;
  padding: 0.6rem 0.9rem;
  border-radius: var(--r);
  font-size: 0.88rem;
  min-height: 2rem;
}
.fb-correct { background: var(--green-dim); color: var(--green); }
.fb-wrong   { background: var(--red-dim); color: var(--red); }

/* ══════════════════════════════════════
   COMMON MISTAKES & TIPS SECTIONS
══════════════════════════════════════ */
.mistakes-list {
  list-style: none;
  padding: 0;
  counter-reset: mistake;
}
.mistakes-list li {
  counter-increment: mistake;
  padding: 0.6rem 0 0.6rem 2.4rem;
  position: relative;
  border-bottom: 1px solid rgba(255,255,255,0.04);
  font-size: 0.93rem;
  line-height: 1.6;
}
.mistakes-list li::before {
  content: counter(mistake);
  position: absolute;
  left: 0;
  width: 1.65rem;
  height: 1.65rem;
  background: rgba(255,77,109,0.12);
  border: 1px solid rgba(255,77,109,0.28);
  border-radius: 50%;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--red);
  text-align: center;
  line-height: 1.65rem;
  top: 0.7rem;
}

.tips-grid {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 1rem;
  margin-top: 1rem;
}
@media (max-width: 700px) { .tips-grid { grid-template-columns: 1fr; } }

.tip-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--r);
  padding: 1.1rem 1.25rem;
}
.tip-card h4 {
  font-size: 0.82rem;
  font-weight: 700;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  margin-bottom: 0.6rem;
}
.tip-card.board h4 { color: var(--amber); }
.tip-card.jee h4   { color: var(--cyan); }
.tip-card.neet h4  { color: var(--green); }
.tip-card p { font-size: 0.88rem; color: var(--text-dim); line-height: 1.6; }