:root {
  --bg: #0f1226;
  --card: #1a1e3a;
  --accent: #6d5dfc;
  --accent-2: #00d4b4;
  --text: #eef0ff;
  --muted: #9aa0c7;
  --danger: #ff6b81;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  background: radial-gradient(1200px 600px at 50% -10%, #20264f 0%, var(--bg) 60%);
  color: var(--text);
  min-height: 100vh;
}
#app { width: 100%; max-width: 520px; margin: 0 auto; padding: 16px; }
.topbar { display: flex; justify-content: space-between; align-items: center; padding: 8px 0 20px; }
.logo { font-weight: 700; font-size: 1.2rem; }
.pill {
  font-size: .72rem; padding: 4px 10px; border-radius: 999px;
  background: #2a2f5a; color: var(--muted);
}
.pill.ok { background: rgba(0,212,180,.15); color: var(--accent-2); }
.pill.err { background: rgba(255,107,129,.15); color: var(--danger); }
.hero { text-align: center; padding: 12px 0 24px; }
.hero h1 { font-size: 1.9rem; margin: 0 0 8px; }
.hero p { color: var(--muted); margin: 0 0 16px; }
.card {
  background: var(--card); border-radius: 18px; padding: 20px;
  box-shadow: 0 10px 40px rgba(0,0,0,.35);
}
.tabs { display: flex; gap: 8px; margin-bottom: 16px; }
.tab {
  flex: 1; padding: 10px; border: 0; border-radius: 12px; cursor: pointer;
  background: #2a2f5a; color: var(--muted); font-weight: 600;
}
.tab.active { background: var(--accent); color: #fff; }
.form { display: flex; flex-direction: column; gap: 10px; }
.form.hidden { display: none; }
.hidden { display: none !important; }
input {
  padding: 13px 14px; border-radius: 12px; border: 1px solid #2f3565;
  background: #11142b; color: var(--text); font-size: 1rem;
}
input:focus { outline: 2px solid var(--accent); border-color: transparent; }
.btn {
  padding: 13px; border: 0; border-radius: 12px; cursor: pointer;
  background: linear-gradient(135deg, var(--accent), #8a7bff);
  color: #fff; font-weight: 700; font-size: 1rem;
}
.btn:active { transform: scale(.98); }
.btn.ghost { background: transparent; border: 1px solid var(--accent); color: var(--text); }
.hint { color: var(--muted); font-size: .82rem; margin: 4px 0 0; }
.msg { margin: 14px 0 0; min-height: 1.2em; font-size: .9rem; }
.msg.ok { color: var(--accent-2); }
.msg.err { color: var(--danger); }

/* ─────────────────────────────────────────────────────────────────────────
   RESPONSIVE — movil-first; se expande con elegancia en tablet y escritorio.
   El uso principal es movil/tablet, pero el escritorio aprovecha el ancho.
   ───────────────────────────────────────────────────────────────────────── */

/* Listas que pasan a rejilla en pantallas anchas */
.lesson-grid { display: grid; grid-template-columns: 1fr; gap: 12px; }

/* Tarjeta de lección del temario (en rejilla) */
.cur-item {
  display: flex; gap: 10px; align-items: flex-start;
  background: var(--card); border: 1px solid #242a52; border-radius: 14px;
  padding: 14px; cursor: pointer; transition: transform .1s, border-color .15s;
}
.cur-item:hover { border-color: var(--accent); transform: translateY(-2px); }
.cur-item .num { color: var(--accent); font-weight: 700; min-width: 1.4em; }
.cur-item .cur-title { font-weight: 600; line-height: 1.3; }
.cur-item .cur-sub { color: var(--accent-2); font-size: .74rem; margin-top: 2px; }
.cur-item .cur-body { flex: 1; min-width: 0; }
.cur-item .code { font-size: .68rem; color: var(--muted); background: #11142b;
  padding: 2px 8px; border-radius: 999px; white-space: nowrap; }

/* Fila de cards (tiles, objetivos, etc.) que se reparte en escritorio */
.dash-cols { display: grid; grid-template-columns: 1fr; gap: 12px; }

/* Anchos comodos de lectura (lecciones, respuestas del tutor) */
.read-narrow { max-width: 760px; margin-inline: auto; }

/* ── Tablet ── */
@media (min-width: 760px) {
  #app { max-width: 1040px; padding: 24px 28px; }
  .lesson-grid { grid-template-columns: repeat(2, 1fr); }
  .dash-cols { grid-template-columns: repeat(2, 1fr); align-items: start; }
  /* formularios y portada no deben estirarse a lo ancho */
  #auth-card, .narrow-card { max-width: 440px; margin-inline: auto; }
  .hero { max-width: 760px; margin-inline: auto; }
  /* contenido de lectura centrado y acotado dentro del ancho grande */
  #lesson-view > .card, #l-blocks, #tutor-out, #result, .blocks { max-width: 820px; margin-inline: auto; }
}

/* ── Escritorio ── */
@media (min-width: 1100px) {
  #app { max-width: 1160px; }
  .lesson-grid { grid-template-columns: repeat(3, 1fr); }
}

/* Chips de filtro (materias, niveles) — global */
.filters { display: flex; gap: 8px; margin: 10px 0; flex-wrap: wrap; }
.filters button {
  padding: 7px 14px; border: 0; border-radius: 999px; cursor: pointer;
  background: #2a2f5a; color: var(--muted); font-weight: 600; font-size: .85rem;
  transition: background .12s, color .12s;
}
.filters button:hover { background: #333a6b; }
.filters button.active { background: var(--accent); color: #fff; }