:root{--bg:#f5f3fa;--card:#fff;--text:#17152a;--muted:#6d687d;--line:#ddd8eb;--accent:#4b3f96;--soft:#eeeafe;--ok:#147348;--okbg:#ddf6e8;--bad:#b1261d;--badbg:#fde5e3;--warn:#8a5900;--warnbg:#fff1cf}*{box-sizing:border-box}html{background:var(--bg)}body{margin:0;background:var(--bg);color:var(--text);font-family:system-ui,-apple-system,Segoe UI,Roboto,Arial,sans-serif}button,select,input{font:inherit}button{border:0;border-radius:12px;padding:13px 14px;font-weight:750;cursor:pointer}button:disabled{opacity:.55;cursor:not-allowed}.hidden{display:none!important}.app{max-width:840px;margin:0 auto;min-height:100vh;padding:16px 14px 44px}.app-header{display:flex;justify-content:space-between;align-items:center;gap:12px;margin-bottom:14px}.app-header h1{font-size:23px;line-height:1.15;margin:0}.app-header p,.muted{font-size:13px;line-height:1.45;color:var(--muted);margin:4px 0 0}.header-actions{display:flex;gap:8px;align-items:center}.panel{background:var(--card);border:1px solid var(--line);border-radius:18px;padding:17px;box-shadow:0 8px 24px rgba(0,0,0,.045)}.stack{display:grid;gap:13px}.topline{display:flex;justify-content:space-between;align-items:center;gap:10px}.topline h2{margin:0 0 6px}.badge{display:inline-flex;align-items:center;background:var(--soft);color:var(--accent);font-size:12px;font-weight:800;padding:7px 10px;border-radius:999px;white-space:nowrap}.stats{display:grid;grid-template-columns:repeat(4,1fr);gap:8px}.stat{background:#f3f6fb;border-radius:12px;padding:11px 5px;text-align:center}.stat b{display:block;font-size:20px}.stat span{font-size:12px;color:var(--muted)}.grid{display:grid;grid-template-columns:1fr 1fr;gap:10px}.field{display:block;font-size:12px;font-weight:750;color:var(--muted)}select,input[type=search]{display:block;width:100%;margin-top:5px;padding:12px;border:1px solid var(--line);border-radius:12px;background:#fff;color:var(--text)}.check-row{display:flex;align-items:flex-start;gap:9px;font-size:14px;color:var(--muted)}.check-row input{width:18px;height:18px;margin-top:1px}.actions,.data-actions{display:grid;grid-template-columns:1fr 1fr;gap:10px}.primary{background:var(--accent);color:#fff}.secondary{background:#e9edf3;color:var(--text)}.ghost{background:transparent;border:1px solid var(--line);color:var(--text)}.good{background:var(--okbg);color:var(--ok)}.bad{background:var(--badbg);color:var(--bad)}.warn{background:var(--warnbg);color:var(--warn)}.notice{padding:12px;border-radius:12px;background:#f5f6f8;color:var(--muted);font-size:13px;line-height:1.5}details{border-top:1px solid var(--line);padding-top:13px}summary{font-weight:800;cursor:pointer}.data-actions{margin-top:12px}.category-stats{display:grid;gap:6px;margin-top:12px}.category-row{display:grid;grid-template-columns:1fr auto;gap:10px;padding:8px 0;border-bottom:1px solid #edf0f4;font-size:13px}.session-topline{margin-top:2px}.progress-wrap{height:10px;background:#e4e8ee;border-radius:999px;overflow:hidden;margin:12px 0 17px}.progress{height:100%;width:0;background:var(--accent);transition:width .2s}.card-scene{perspective:1100px}.flashcard{position:relative;min-height:460px;transform-style:preserve-3d;transition:transform .42s;cursor:pointer}.flashcard.flipped{transform:rotateY(180deg)}.flashcard.no-transition{transition:none!important}.face{position:absolute;inset:0;display:flex;flex-direction:column;align-items:center;justify-content:center;text-align:center;padding:25px;border:1px solid var(--line);border-radius:23px;background:var(--card);backface-visibility:hidden;box-shadow:0 12px 34px rgba(0,0,0,.06)}.back{transform:rotateY(180deg)}.meta{display:flex;gap:7px;flex-wrap:wrap;justify-content:center;margin-bottom:17px}.pill{font-size:11px;font-weight:850;letter-spacing:.04em;text-transform:uppercase;padding:6px 8px;border-radius:999px;background:var(--soft);color:var(--accent)}.pill.neutral{background:#f0f1f4;color:#5a606a}.question{font-size:27px;line-height:1.25;font-weight:850}.answer{font-size:29px;line-height:1.22;font-weight:850;margin-bottom:18px}.explanation-box{width:100%;padding:14px;border-radius:14px;background:#f4f7fc;text-align:left;line-height:1.5}.explanation-box strong{display:block;color:var(--accent);font-size:13px;margin-bottom:5px}.explanation-box p{margin:0;font-size:15px;color:#454c56}.source{margin-top:13px;font-size:11px;color:#8a9099}.tap{position:absolute;bottom:17px;font-size:13px;color:var(--muted)}.rating{display:grid;grid-template-columns:1fr 1fr 1fr;gap:9px;margin-top:13px}.quiz-card{background:var(--card);border:1px solid var(--line);border-radius:23px;padding:22px;box-shadow:0 12px 34px rgba(0,0,0,.06)}.quiz-question{font-size:25px;line-height:1.3;font-weight:850;margin:18px 0 20px;text-align:center}.quiz-options{display:grid;gap:10px}.quiz-option{width:100%;text-align:left;background:#f3f5f8;border:1px solid transparent;color:var(--text)}.quiz-option.correct{background:var(--okbg);border-color:#79c7a2;color:var(--ok)}.quiz-option.wrong{background:var(--badbg);border-color:#e6a19b;color:var(--bad)}.quiz-option.dimmed{opacity:.58}.quiz-feedback{margin-top:14px;padding:14px;border-radius:13px;background:#f5f6f8;line-height:1.5}.quiz-feedback .explain-title{display:block;margin-top:9px;color:var(--accent)}.full{width:100%;margin-top:13px}.finish-score{font-size:42px;font-weight:900;margin:8px 0}footer{margin-top:18px;text-align:center;font-size:12px;color:var(--muted)}.loading-screen{min-height:100vh;display:flex;flex-direction:column;align-items:center;justify-content:center;gap:10px;padding:24px;text-align:center;color:var(--text)}.loading-screen span{color:var(--muted);font-size:13px}.loader{width:42px;height:42px;border:4px solid #dbe4f5;border-top-color:var(--accent);border-radius:50%;animation:spin .8s linear infinite}@keyframes spin{to{transform:rotate(360deg)}}@media(max-width:600px){.app-header{align-items:flex-start}.header-actions{flex-direction:column}.stats{grid-template-columns:repeat(2,1fr)}.grid,.actions,.data-actions{grid-template-columns:1fr}.rating{grid-template-columns:1fr}.flashcard{min-height:520px}.question,.quiz-question{font-size:24px}.answer{font-size:26px}.topline{align-items:flex-start}}
.brand{display:flex;align-items:center;gap:11px}.brand-icon{width:48px;height:48px;border-radius:14px;box-shadow:0 8px 22px rgba(53,45,115,.22)}
.loading-logo{width:78px;height:78px;border-radius:22px;box-shadow:0 12px 34px rgba(53,45,115,.22);margin-bottom:6px}


.logo-svg{display:inline-flex;overflow:hidden;flex:0 0 auto;background:#4B3F96}
.logo-svg svg{display:block;width:100%;height:100%}

.install-unavailable{
  margin-top:8px;
  font-size:12px;
  line-height:1.4;
  color:var(--muted);
}

/* Promoción de instalación: patrón no bloqueante inspirado en web.dev */
.install-banner{
  position:fixed;
  z-index:60;
  left:50%;
  bottom:max(14px,env(safe-area-inset-bottom));
  transform:translateX(-50%);
  width:min(680px,calc(100% - 24px));
  display:grid;
  grid-template-columns:auto minmax(0,1fr) auto auto;
  align-items:center;
  gap:11px;
  padding:11px 12px;
  background:rgba(255,255,255,.98);
  border:1px solid var(--line);
  border-radius:17px;
  box-shadow:0 15px 45px rgba(38,31,86,.22);
  backdrop-filter:blur(14px);
  animation:install-enter .24s ease-out;
}
@keyframes install-enter{
  from{opacity:0;transform:translate(-50%,18px)}
  to{opacity:1;transform:translate(-50%,0)}
}
.install-banner-icon{
  width:46px;
  height:46px;
  border-radius:13px;
}
.install-banner-copy{
  display:grid;
  gap:2px;
  min-width:0;
}
.install-banner-copy strong{
  font-size:15px;
  line-height:1.25;
}
.install-banner-copy span{
  font-size:12.5px;
  line-height:1.35;
  color:var(--muted);
}
.install-banner-primary{
  padding:10px 14px;
  white-space:nowrap;
}
.install-banner-close{
  display:grid;
  place-items:center;
  width:34px;
  height:34px;
  padding:0;
  border-radius:50%;
  background:transparent;
  color:var(--muted);
  font-size:25px;
  font-weight:400;
  line-height:1;
}
.install-banner-close:active{
  background:#eeeaf8;
}
@media(max-width:600px){
  .brand-icon{width:44px;height:44px}
  .install-banner{
    grid-template-columns:auto minmax(0,1fr) auto;
    gap:9px;
  }
  .install-banner-primary{
    grid-column:2/3;
    justify-self:start;
    padding:9px 14px;
  }
  .install-banner-close{
    grid-column:3;
    grid-row:1;
  }
  .app{padding-bottom:126px}
}

/* ==========================================================
   Pantalla principal simplificada · v6
   ========================================================== */
.visually-hidden{
  position:absolute!important;
  width:1px!important;
  height:1px!important;
  padding:0!important;
  margin:-1px!important;
  overflow:hidden!important;
  clip:rect(0,0,0,0)!important;
  white-space:nowrap!important;
  border:0!important;
}
.home-layout{
  display:grid;
  gap:15px;
}
.welcome-panel{
  padding:20px;
  border-radius:24px;
  color:#fff;
  background:
    radial-gradient(circle at 90% 10%,rgba(243,198,78,.28),transparent 32%),
    linear-gradient(145deg,#51449f,#352d73);
  box-shadow:0 16px 38px rgba(53,45,115,.22);
}
.welcome-heading{
  display:flex;
  justify-content:space-between;
  align-items:flex-start;
  gap:18px;
}
.welcome-heading h2{
  margin:4px 0 5px;
  font-size:28px;
}
.welcome-heading p{
  margin:0;
  color:rgba(255,255,255,.78);
  line-height:1.45;
}
.eyebrow{
  display:block;
  color:var(--accent);
  font-size:11px;
  font-weight:850;
  letter-spacing:.09em;
  text-transform:uppercase;
}
.welcome-panel .eyebrow{
  color:#f3d575;
}
.question-count{
  min-width:104px;
  padding:11px 13px;
  border:1px solid rgba(255,255,255,.18);
  border-radius:16px;
  background:rgba(255,255,255,.1);
  text-align:center;
}
.question-count strong{
  display:block;
  font-size:23px;
}
.question-count span{
  display:block;
  margin-top:2px;
  font-size:11px;
  line-height:1.25;
  color:rgba(255,255,255,.74);
}
.quick-actions{
  display:grid;
  grid-template-columns:1fr 1fr;
  gap:10px;
  margin-top:18px;
}
.quick-action{
  display:grid;
  grid-template-columns:auto minmax(0,1fr) auto;
  align-items:center;
  gap:11px;
  min-height:76px;
  padding:12px;
  border:1px solid rgba(255,255,255,.14);
  color:#fff;
  background:rgba(255,255,255,.10);
  text-align:left;
}
.quick-action-featured{
  color:#2c255e;
  background:#fff;
}
.quick-action:disabled{
  opacity:.55;
}
.quick-action-icon{
  display:grid;
  place-items:center;
  width:39px;
  height:39px;
  border-radius:12px;
  color:#4b3f96;
  background:#f3c64e;
  font-size:20px;
}
.quick-action-icon-soft{
  color:#fff;
  background:rgba(255,255,255,.17);
}
.quick-action-featured .quick-action-icon-soft{
  color:#4b3f96;
}
.quick-action-copy{
  display:grid;
  gap:3px;
}
.quick-action-copy strong{
  font-size:14px;
  line-height:1.25;
}
.quick-action-copy small{
  color:rgba(255,255,255,.72);
  font-size:11.5px;
  line-height:1.25;
}
.quick-action-featured .quick-action-copy small{
  color:#736d82;
}
.quick-action-arrow{
  font-size:28px;
  font-weight:400;
  opacity:.75;
}
.builder-panel,.progress-panel{
  border-radius:22px;
}
.section-heading{
  display:flex;
  justify-content:space-between;
  align-items:flex-start;
  gap:12px;
  margin-bottom:18px;
}
.section-heading h3{
  margin:4px 0 0;
  font-size:21px;
}
.builder-block{
  display:grid;
  gap:9px;
  margin-bottom:17px;
}
.builder-label,.friendly-field>span,.advanced-grid .field>span{
  color:#55505f;
  font-size:13px;
  font-weight:780;
}
.mode-choices{
  display:grid;
  grid-template-columns:1fr 1fr;
  gap:9px;
}
.mode-choice{
  display:grid;
  gap:4px;
  min-height:78px;
  padding:13px;
  border:1px solid var(--line);
  color:var(--text);
  background:#f7f8fb;
  text-align:left;
}
.mode-choice strong{
  font-size:14px;
}
.mode-choice small{
  color:var(--muted);
  font-size:11.5px;
  line-height:1.35;
}
.mode-choice.active{
  border-color:#8d82d0;
  background:#f0edff;
  box-shadow:0 0 0 2px rgba(75,63,150,.10);
}
.friendly-field{
  display:grid;
  gap:8px;
  margin-bottom:17px;
}
.duration-choices{
  display:grid;
  grid-template-columns:repeat(4,1fr);
  gap:8px;
}
.duration-choice{
  display:grid;
  gap:1px;
  padding:11px 7px;
  border:1px solid var(--line);
  color:var(--text);
  background:#f7f8fb;
}
.duration-choice strong{
  font-size:19px;
}
.duration-choice span{
  color:var(--muted);
  font-size:10.5px;
}
.duration-choice.active{
  color:#fff;
  border-color:#4b3f96;
  background:#4b3f96;
}
.duration-choice.active span{
  color:rgba(255,255,255,.76);
}
.session-summary{
  margin:5px 0 13px;
  padding:10px 12px;
  border-radius:12px;
  color:#5a536b;
  background:#f5f3fa;
  font-size:12.5px;
  line-height:1.4;
  text-align:center;
}
.start-session-button{
  width:100%;
  min-height:52px;
  font-size:16px;
}
.text-action{
  width:100%;
  padding:11px;
  color:var(--accent);
  background:transparent;
  font-size:13px;
}
.advanced-options{
  margin-top:8px;
  padding-top:13px;
  border-top:1px solid var(--line);
}
.advanced-options summary,.account-options summary{
  cursor:pointer;
  color:#514b5b;
  font-size:14px;
  font-weight:780;
}
.advanced-grid{
  display:grid;
  grid-template-columns:1fr 1fr;
  gap:10px;
  margin-top:14px;
}
.progress-heading{
  margin-bottom:12px;
}
.friendly-stats{
  margin:0;
}
.friendly-stats .stat{
  padding:13px 7px;
}
.account-options{
  border-radius:19px;
}
.settings-copy{
  margin:10px 0 13px;
}
.danger-ghost{
  color:#a52b24;
  border:1px solid #efcbc8;
  background:#fff6f5;
}
.category-row strong{
  color:#5f5869;
}
@media(max-width:600px){
  .welcome-panel{
    padding:17px;
    border-radius:21px;
  }
  .welcome-heading{
    align-items:center;
  }
  .welcome-heading h2{
    font-size:24px;
  }
  .question-count{
    min-width:88px;
  }
  .question-count strong{
    font-size:19px;
  }
  .quick-actions{
    grid-template-columns:1fr;
  }
  .mode-choices{
    grid-template-columns:1fr;
  }
  .duration-choices{
    grid-template-columns:repeat(4,1fr);
  }
  .advanced-grid{
    grid-template-columns:1fr;
  }
}

.rating button.is-saving{
  opacity:.68;
  cursor:wait;
}
.session-save-warning{
  position:fixed;
  left:50%;
  bottom:max(14px,env(safe-area-inset-bottom));
  transform:translateX(-50%);
  z-index:80;
  width:min(560px,calc(100% - 24px));
  padding:11px 14px;
  border:1px solid #efcbc8;
  border-radius:14px;
  color:#84221c;
  background:#fff6f5;
  box-shadow:0 12px 32px rgba(91,31,24,.16);
  font-size:13px;
  line-height:1.4;
  text-align:center;
}

.mode-availability-note{
  margin:0;
  padding:9px 11px;
  border-radius:11px;
  color:#625b70;
  background:#f5f3fa;
  font-size:12px;
  line-height:1.4;
}

/* Explicaciones didácticas v9 */
.explanation-box p,
.quiz-feedback{
  line-height:1.58;
}
.explanation-box strong,
.explain-title{
  letter-spacing:.01em;
}

/* Opciones de test en sentence case · v10 */
.quiz-option{
  text-transform:none;
}