/* POTENCIAL ELÉTRICO — Estudo Dirigido — Estilo claro com identidade azul-índigo */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --bg:        #f4f7ff;
  --bg2:       #eaeffc;
  --surface:   #ffffff;
  --border:    #d4dcf5;
  --border2:   #b8c4e8;
  --accent:    #4361ee;
  --accent-d:  #2f4ac7;
  --accent2:   #2563eb;
  --accent3:   #c0392b;
  --plus:      #2c6e49;
  --minus:     #c0392b;
  --text:      #12183d;
  --text-mid:  #3a4470;
  --text-muted:#7480a8;
  --font-serif:'Playfair Display', Georgia, serif;
  --font-body: 'Barlow', sans-serif;
  --font-cond: 'Barlow Condensed', sans-serif;
  --r:         10px;
  --r-lg:      18px;
}

html { scroll-behavior: smooth; }

body {
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.75;
}

/* === SKIP LINK === */
.skip-link {
  position: absolute; top: -100%; left: 0;
  background: var(--accent); color: #fff;
  padding: 10px 20px; font-size: .85rem; font-weight: 600;
  z-index: 9999; border-radius: 0 0 8px 0; text-decoration: none; transition: top .15s;
}
.skip-link:focus { top: 0; outline: 3px solid var(--accent2); outline-offset: 2px; }

/* === HERO === */
.hero {
  min-height: 100vh;
  position: relative;
  display: grid; grid-template-columns: 1fr 1fr;
  align-items: center; overflow: hidden;
  padding: 80px 6vw 60px; gap: 40px;
  background: #0d1235;
}

.hero-bg { position: absolute; inset: 0; z-index: 0; pointer-events: none; }

.hero-grid {
  position: absolute; inset: 0;
  background-image:
    linear-gradient(rgba(67,97,238,.06) 1px, transparent 1px),
    linear-gradient(90deg, rgba(67,97,238,.06) 1px, transparent 1px);
  background-size: 60px 60px;
}

.hero-glow {
  position: absolute;
  width: 500px; height: 500px;
  background: radial-gradient(circle, rgba(67,97,238,.25) 0%, transparent 70%);
  top: -100px; right: -100px;
  border-radius: 50%;
}

.hero-content { position: relative; z-index: 1; }

.hero-eyebrow {
  display: flex; align-items: center; gap: 14px; margin-bottom: 28px;
  font-family: var(--font-cond); font-size: .78rem;
  letter-spacing: .18em; text-transform: uppercase; color: var(--accent);
}
.eyebrow-line {
  display: block; width: 36px; height: 1px;
  background: var(--accent); opacity: .6;
}

.hero-title { margin-bottom: 20px; line-height: 1; }
.ht-small {
  display: block; font-family: var(--font-cond); font-weight: 400;
  font-size: clamp(.85rem, 2vw, 1rem); letter-spacing: .2em; text-transform: uppercase;
  color: rgba(255,255,255,.45); margin-bottom: 10px;
}
.ht-big {
  display: block; font-family: var(--font-serif);
  font-size: clamp(3rem, 9vw, 6.5rem);
  font-weight: 900; color: #fff; line-height: .95;
}
.ht-big em { font-style: italic; color: var(--accent); }

.hero-desc {
  color: rgba(255,255,255,.5); font-size: 1rem;
  max-width: 460px; margin: 0 auto 36px; font-weight: 300; line-height: 1.8;
}

.hero-cta {
  display: inline-block; background: var(--accent); color: #fff;
  font-family: var(--font-cond); font-weight: 700; font-size: .88rem;
  letter-spacing: .1em; text-transform: uppercase;
  padding: 14px 34px; text-decoration: none; border-radius: 4px;
  transition: background .2s, transform .2s;
}
.hero-cta:hover { background: var(--accent-d); transform: translateY(-3px); }

.hero-formula { position: relative; z-index: 1; display: flex; align-items: center; justify-content: center; }
.formula-big {
  font-family: 'Courier New', monospace;
  font-size: clamp(.9rem, 2vw, 1.35rem);
  color: var(--accent); background: rgba(255,255,255,.04);
  padding: 28px 36px; border-radius: var(--r-lg);
  border: 1px solid rgba(67,97,238,.3);
  box-shadow: 0 0 40px rgba(67,97,238,.1);
  text-align: left; line-height: 2.4;
}

/* === SUMÁRIO === */
.sumario {
  background: var(--text);
  padding: 0 5vw;
  position: sticky; top: 0; z-index: 100;
}
.sumario-wrap {
  display: flex; align-items: center; gap: 24px;
  overflow-x: auto; scrollbar-width: none; height: 52px;
}
.sumario-wrap::-webkit-scrollbar { display: none; }

.sum-label {
  font-family: var(--font-cond); font-size: .65rem;
  text-transform: uppercase; letter-spacing: .15em;
  color: rgba(255,255,255,.3); white-space: nowrap;
}
.sumario-logo-link {
  display: flex; align-items: center; text-decoration: none; transition: opacity .2s;
}
.sumario-logo-link:hover { opacity: .7; }
.sumario-logo { height: 32px; width: auto; display: block; }

.sum-list { display: flex; list-style: none; gap: 2px; }
.sum-list a {
  display: block; padding: 6px 14px;
  font-family: var(--font-cond); font-size: .8rem;
  letter-spacing: .05em; text-transform: uppercase;
  color: rgba(255,255,255,.5); text-decoration: none;
  border-radius: 3px; white-space: nowrap;
  transition: background .15s, color .15s;
}
.sum-list a:hover { background: rgba(67,97,238,.2); color: var(--accent); }

/* === MAIN === */
.main { max-width: 880px; margin: 0 auto; padding: 60px 24px 80px; }

/* === TOPIC === */
.topic {
  margin-bottom: 90px;
  opacity: 0; transform: translateY(28px);
  transition: opacity .6s ease, transform .6s ease;
}
.topic.visible { opacity: 1; transform: translateY(0); }

.topic-head {
  display: flex; align-items: flex-start; gap: 20px;
  margin-bottom: 32px; padding-bottom: 20px;
  border-bottom: 2px solid var(--border);
}

.t-num {
  font-family: var(--font-serif); font-size: 3.5rem; font-weight: 900;
  color: var(--accent); opacity: .22; line-height: 1;
  flex-shrink: 0; min-width: 70px;
}
.topic-head h2 {
  font-family: var(--font-serif);
  font-size: clamp(1.6rem, 4vw, 2.2rem);
  font-weight: 700; line-height: 1.1; color: var(--text); margin-bottom: 4px;
}
.t-tag {
  font-family: var(--font-cond); font-size: .7rem;
  letter-spacing: .15em; text-transform: uppercase; color: var(--text-muted);
}

.topic-body > p { color: var(--text-mid); margin-bottom: 20px; font-size: 1rem; }
.topic-body > p strong { color: var(--text); }
.topic-body > p em { color: var(--accent); font-style: italic; }

/* === HIGHLIGHT === */
.highlight {
  display: flex; gap: 16px;
  background: rgba(67,97,238,.06);
  border-left: 3px solid var(--accent);
  border-radius: 0 var(--r) var(--r) 0;
  padding: 18px 20px; margin: 22px 0;
}
.highlight.warning {
  background: rgba(200,169,81,.07);
  border-left-color: #b8962e;
}
.hl-icon { font-size: 1.4rem; flex-shrink: 0; margin-top: 2px; }
.highlight > div { flex: 1; }
.highlight strong { color: var(--text); font-weight: 600; }
.highlight ul { margin-top: 8px; padding-left: 18px; }
.highlight li { font-size: .92rem; color: var(--text-mid); margin-bottom: 4px; }
.highlight code {
  font-family: 'Courier New', monospace; font-size: .88rem;
  background: rgba(0,0,0,.06); padding: 2px 6px; border-radius: 3px;
}

/* === FORMULA BOXES === */
.formula-row { display: flex; gap: 16px; flex-wrap: wrap; margin: 22px 0; }
.fbox {
  flex: 1; min-width: 200px; background: var(--text); color: #fff;
  border-radius: var(--r); padding: 16px 20px;
  display: flex; flex-direction: column; gap: 4px;
}
.fbox.wide { flex: 100%; min-width: 100%; }
.flabel { font-family: var(--font-cond); font-size: .65rem; letter-spacing: .15em; text-transform: uppercase; color: rgba(255,255,255,.45); }
.fval { font-family: var(--font-serif); font-size: 1.15rem; color: var(--accent); }
.funit { font-size: .75rem; color: rgba(255,255,255,.4); font-family: var(--font-cond); }

/* === FORMULA DESTAQUE === */
.formula-destaque {
  background: var(--text); border-radius: var(--r-lg);
  padding: 32px 36px; margin: 24px 0;
  display: flex; flex-direction: column; gap: 10px;
  align-items: center; text-align: center; position: relative; overflow: hidden;
}
.formula-destaque::before {
  content: ''; position: absolute; top: 0; left: 0; right: 0; height: 3px;
  background: linear-gradient(90deg, transparent, var(--accent), transparent);
}
.fd-label { font-family: var(--font-cond); font-size: .7rem; letter-spacing: .2em; text-transform: uppercase; color: rgba(255,255,255,.35); }
.fd-eq { font-family: var(--font-serif); font-size: clamp(1.6rem, 4vw, 2.6rem); color: var(--accent); font-style: italic; }
.fd-vars { display: flex; flex-wrap: wrap; gap: 12px 24px; justify-content: center; margin-top: 6px; }
.fd-vars span { font-size: .82rem; color: rgba(255,255,255,.55); font-family: var(--font-cond); letter-spacing: .04em; }
.fd-vars strong { color: rgba(255,255,255,.85); }

/* === CONCEPT BOX === */
.concept-box {
  background: var(--bg2); border: 1px solid var(--border);
  border-radius: var(--r); padding: 18px 22px; margin: 18px 0;
}
.concept-box h4 {
  font-family: var(--font-cond); font-size: .78rem;
  letter-spacing: .12em; text-transform: uppercase;
  color: var(--accent-d); margin-bottom: 8px;
}
.concept-box p { font-size: .9rem; color: var(--text-mid); }
.concept-box ul { list-style: none; display: flex; flex-direction: column; gap: 8px; padding: 0; margin-top: 8px; }
.concept-box li { font-size: .9rem; color: var(--text-mid); padding-left: 20px; position: relative; }
.concept-box li::before { content: '—'; position: absolute; left: 0; color: var(--accent); }

/* === EXAMPLE BOX === */
.example-box {
  background: rgba(67,97,238,.05);
  border-left: 3px solid var(--accent2);
  border-radius: 0 var(--r) var(--r) 0;
  padding: 18px 22px; margin: 22px 0;
}
.example-box h4 {
  font-family: var(--font-cond); font-size: .78rem;
  letter-spacing: .12em; text-transform: uppercase;
  color: var(--accent2); margin-bottom: 12px;
}
.example-box p {
  font-size: .88rem; color: var(--text-mid);
  margin-bottom: 6px; font-family: 'Courier New', monospace;
}
.example-box p strong { color: var(--text); }

/* === ANALOGY GRID === */
.analogy-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; margin: 24px 0; }
.analogy-card {
  background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--r); padding: 18px 20px;
}
.analogy-card.grav { border-top: 3px solid #60a5fa; }
.analogy-card.elet { border-top: 3px solid var(--accent); }
.analogy-card h4 { font-size: .8rem; font-family: var(--font-cond); letter-spacing: .08em; text-transform: uppercase; margin-bottom: 12px; }
.analogy-card.grav h4 { color: #3b82f6; }
.analogy-card.elet h4 { color: var(--accent); }
.analogy-card ul { list-style: none; display: flex; flex-direction: column; gap: 6px; }
.analogy-card li { font-size: .88rem; color: var(--text-mid); padding-left: 14px; position: relative; }
.analogy-card li::before { content: '→'; position: absolute; left: 0; font-size: .8rem; }
.analogy-card.grav li::before { color: #3b82f6; }
.analogy-card.elet li::before { color: var(--accent); }

/* === COMPARE TABLE === */
.compare-table { border: 1px solid var(--border); border-radius: var(--r); overflow: hidden; margin: 24px 0; font-size: .88rem; }
.ct-head {
  display: grid; grid-template-columns: 160px 1fr 1fr;
  background: var(--text); color: #fff;
  font-family: var(--font-cond); font-size: .78rem;
  letter-spacing: .1em; text-transform: uppercase;
  padding: 10px 16px; gap: 16px;
}
.ct-row {
  display: grid; grid-template-columns: 160px 1fr 1fr;
  gap: 16px; padding: 12px 16px;
  border-top: 1px solid var(--border); align-items: start;
}
.ct-row:nth-child(even) { background: var(--bg2); }
.ct-label { font-weight: 600; color: var(--text); font-size: .82rem; }
.ct-val   { color: var(--accent); font-family: var(--font-cond); font-weight: 600; }
.ct-row span { color: var(--text-mid); }

/* === QUIZ === */
.quiz-zone {
  background: var(--surface); border: 1px solid var(--border);
  border-top: 3px solid var(--accent);
  border-radius: var(--r-lg); padding: 28px 32px; margin-top: 36px;
}
.quiz-header {
  font-family: var(--font-cond); font-size: .7rem;
  letter-spacing: .18em; text-transform: uppercase;
  color: var(--accent); margin-bottom: 22px;
  display: flex; align-items: center; gap: 12px;
}
.quiz-header::after { content: ''; flex: 1; height: 1px; background: var(--border); }

.q-block { margin-bottom: 28px; padding-bottom: 26px; border-bottom: 1px solid var(--border); }
.q-block:last-child { border-bottom: none; margin-bottom: 0; padding-bottom: 0; }

.q-num {
  font-family: var(--font-cond); font-size: .68rem;
  letter-spacing: .15em; text-transform: uppercase;
  color: var(--text-muted); display: block; margin-bottom: 6px;
}
.q-text { font-size: .97rem; color: var(--text); margin-bottom: 14px; line-height: 1.7; }

.opts { display: flex; flex-direction: column; gap: 8px; }
.opt-btn {
  background: var(--bg); border: 1px solid var(--border); color: var(--text-mid);
  font-family: var(--font-body); font-size: .88rem; padding: 10px 16px;
  border-radius: var(--r); cursor: pointer; text-align: left;
  display: flex; align-items: center; gap: 12px;
  transition: border-color .15s, background .15s;
}
.opt-btn:hover:not(:disabled) { border-color: var(--accent); background: rgba(67,97,238,.05); color: var(--text); }
.opt-btn.correct { border-color: var(--plus); background: rgba(44,110,73,.08); color: var(--plus); }
.opt-btn.wrong   { border-color: var(--minus); background: rgba(192,57,43,.08); color: var(--minus); }
.opt-btn:disabled { cursor: default; }

.opt-ltr {
  font-family: var(--font-cond); font-weight: 700; font-size: .72rem;
  width: 22px; height: 22px; border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  border: 1px solid currentColor; flex-shrink: 0; opacity: .7;
}

.num-row { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.num-inp {
  background: var(--bg); border: 1px solid var(--border); color: var(--text);
  font-family: var(--font-body); font-size: .97rem; padding: 9px 14px;
  border-radius: var(--r); width: 150px; transition: border-color .2s; outline: none;
}
.num-inp:focus { border-color: var(--accent); background: #fff; }
.num-unit { font-family: var(--font-cond); font-size: .78rem; color: var(--text-muted); letter-spacing: .05em; }

.ver-btn {
  background: transparent; border: 1px solid var(--accent); color: var(--accent-d);
  font-family: var(--font-cond); font-size: .75rem; letter-spacing: .1em; text-transform: uppercase;
  padding: 9px 18px; border-radius: var(--r); cursor: pointer;
  transition: background .15s, color .15s;
}
.ver-btn:hover { background: var(--accent); color: #fff; }
.ver-btn:disabled { opacity: .5; cursor: default; }

.fb {
  margin-top: 10px; font-size: .85rem; padding: 10px 14px;
  border-radius: var(--r); display: none; font-family: var(--font-body); line-height: 1.6;
}
.fb.show  { display: block; }
.fb.certo { color: var(--plus); background: rgba(44,110,73,.08); border: 1px solid rgba(44,110,73,.25); }
.fb.erro  { color: var(--minus); background: rgba(192,57,43,.08); border: 1px solid rgba(192,57,43,.2); }

/* === PLACAR === */
.placar-section { background: var(--text); padding: 80px 24px; }
.placar-inner { max-width: 500px; margin: 0 auto; text-align: center; }
.placar-inner h2 { font-family: var(--font-serif); font-size: 2.2rem; color: #fff; margin-bottom: 36px; }

.placar-display {
  display: flex; align-items: center; justify-content: center;
  gap: 40px; flex-wrap: wrap;
}
.pd-ring { position: relative; width: 130px; height: 130px; flex-shrink: 0; }
.ring-svg { width: 100%; height: 100%; }
.pd-nums {
  position: absolute; inset: 0;
  display: flex; align-items: center; justify-content: center; gap: 4px;
}
#p-score { font-family: var(--font-serif); font-size: 2.6rem; color: var(--accent); line-height: 1; }
.pd-sep { font-family: var(--font-serif); font-size: 1.6rem; color: rgba(255,255,255,.2); }
#p-total { font-family: var(--font-serif); font-size: 2.6rem; color: rgba(255,255,255,.25); line-height: 1; }

.pd-info { text-align: left; max-width: 280px; }
#p-msg { color: rgba(255,255,255,.55); font-size: .92rem; margin-bottom: 20px; line-height: 1.7; }

.reset-btn {
  background: transparent; border: 1px solid rgba(255,255,255,.2);
  color: rgba(255,255,255,.4); font-family: var(--font-cond); font-size: .75rem;
  letter-spacing: .12em; text-transform: uppercase; padding: 9px 20px;
  border-radius: var(--r); cursor: pointer; transition: border-color .2s, color .2s;
}
.reset-btn:hover { border-color: var(--minus); color: #e07070; }

.report-name { margin-top: 18px; }
.report-hint-e {
  display: block; color: rgba(255,255,255,.35); font-family: var(--font-cond);
  font-size: .7rem; letter-spacing: .1em; text-transform: uppercase; margin-bottom: 6px;
}
.name-input {
  display: block; width: 100%; max-width: 260px; margin-top: 4px;
  background: rgba(255,255,255,.07); border: 1px solid rgba(255,255,255,.15);
  border-radius: var(--r); color: rgba(255,255,255,.8);
  font-family: var(--font-body); font-size: .88rem;
  padding: 9px 12px; outline: none; transition: border-color .2s;
}
.name-input:focus { border-color: var(--accent); }
.name-input::placeholder { color: rgba(255,255,255,.25); }

.report-actions-e { margin-top: 20px; }
.report-btns-e { display: flex; gap: 8px; flex-wrap: wrap; margin-top: 8px; }
.report-btn-e {
  background: transparent; border: 1px solid rgba(255,255,255,.15);
  color: rgba(255,255,255,.4); font-family: var(--font-cond); font-size: .72rem;
  padding: 8px 14px; border-radius: var(--r); cursor: pointer;
  letter-spacing: .08em; text-transform: uppercase; transition: border-color .2s, color .2s;
}
.report-btn-e:hover { border-color: var(--accent); color: var(--accent); }

/* === FOOTER === */
.footer {
  background: #090c22; padding: 20px; text-align: center;
  font-family: var(--font-cond); font-size: .65rem;
  letter-spacing: .15em; text-transform: uppercase; color: rgba(255,255,255,.2);
}

/* === RESPONSIVE === */
@media (max-width: 768px) {
  .hero { grid-template-columns: 1fr; padding: 80px 5vw 50px; }
  .hero-formula { display: none; }
  .analogy-grid { grid-template-columns: 1fr; }
  .ct-head, .ct-row { grid-template-columns: 100px 1fr 1fr; font-size: .78rem; }
  .quiz-zone { padding: 20px 18px; }
  .placar-display { flex-direction: column; align-items: center; }
  .pd-info { text-align: center; }
}
@media (max-width: 500px) {
  .formula-row { flex-direction: column; }
  .fbox { min-width: 100%; }
}