/* ── Reset & Base ── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }

:root {
  --green:   #2e7d32;
  --green-l: #4caf50;
  --green-xl:#e8f5e9;
  --blue:    #1565c0;
  --blue-l:  #1e88e5;
  --blue-xl: #e3f2fd;
  --amber:   #f57f17;
  --amber-xl:#fff8e1;
  --red:     #c62828;
  --red-xl:  #ffebee;
  --grey:    #546e7a;
  --light:   #f5f7fa;
  --white:   #ffffff;
  --shadow:  0 2px 12px rgba(0,0,0,.1);
  --radius:  12px;
}

body {
  font-family: 'Segoe UI', system-ui, sans-serif;
  background: var(--light);
  color: #212121;
  min-height: 100vh;
}

/* ── Nav ── */
nav {
  background: var(--green);
  padding: .9rem 1.5rem;
  display: flex;
  align-items: center;
  justify-content: space-between;
  box-shadow: 0 2px 6px rgba(0,0,0,.2);
}
nav .brand {
  color: #fff;
  font-size: 1.2rem;
  font-weight: 700;
  text-decoration: none;
  display: flex;
  align-items: center;
  gap: .5rem;
}
nav .nav-links { display: flex; gap: 1rem; align-items: center; }
nav .nav-links a {
  color: rgba(255,255,255,.85);
  text-decoration: none;
  font-size: .9rem;
  padding: .35rem .7rem;
  border-radius: 6px;
  transition: background .2s;
}
nav .nav-links a:hover { background: rgba(255,255,255,.15); color: #fff; }

/* ── Container ── */
.container { max-width: 880px; margin: 0 auto; padding: 2rem 1rem; }
.container-sm { max-width: 480px; margin: 0 auto; padding: 2rem 1rem; }

/* ── Cards ── */
.card {
  background: var(--white);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1.8rem;
  margin-bottom: 1.5rem;
}
.card-title {
  font-size: 1.1rem;
  font-weight: 700;
  margin-bottom: 1rem;
  color: var(--green);
}

/* ── Buttons ── */
.btn {
  display: inline-block;
  padding: .65rem 1.4rem;
  border: none;
  border-radius: 8px;
  font-size: .95rem;
  font-weight: 600;
  cursor: pointer;
  text-decoration: none;
  transition: filter .2s, transform .1s;
}
.btn:hover  { filter: brightness(1.08); }
.btn:active { transform: scale(.97); }

.btn-green  { background: var(--green);  color: #fff; }
.btn-blue   { background: var(--blue);   color: #fff; }
.btn-outline {
  background: transparent;
  border: 2px solid var(--green);
  color: var(--green);
}
.btn-outline:hover { background: var(--green-xl); }
.btn-danger { background: var(--red); color: #fff; }
.btn-sm     { padding: .4rem 1rem; font-size: .85rem; }
.btn-lg     { padding: .85rem 2rem; font-size: 1.05rem; }
.btn-block  { display: block; width: 100%; text-align: center; }

/* ── Forms ── */
.form-group { margin-bottom: 1.2rem; }
label { display: block; font-weight: 600; margin-bottom: .4rem; font-size: .9rem; }
input[type=text], input[type=password] {
  width: 100%;
  padding: .7rem 1rem;
  border: 2px solid #cfd8dc;
  border-radius: 8px;
  font-size: 1rem;
  transition: border-color .2s;
}
input:focus { outline: none; border-color: var(--green-l); }

/* ── Alerts ── */
.alert {
  padding: .85rem 1.2rem;
  border-radius: 8px;
  margin-bottom: 1rem;
  font-size: .92rem;
}
.alert-error   { background: var(--red-xl);   color: var(--red);   border-left: 4px solid var(--red); }
.alert-success { background: var(--green-xl); color: var(--green); border-left: 4px solid var(--green); }

/* ── Stat tiles ── */
.stats-row { display: flex; gap: 1rem; flex-wrap: wrap; margin-bottom: 1.5rem; }
.stat-tile {
  flex: 1 1 130px;
  background: var(--white);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 1.2rem;
  text-align: center;
}
.stat-tile .stat-val {
  font-size: 2rem;
  font-weight: 800;
  color: var(--green);
  line-height: 1;
}
.stat-tile .stat-lbl {
  font-size: .78rem;
  color: var(--grey);
  margin-top: .35rem;
  text-transform: uppercase;
  letter-spacing: .04em;
}
.streak-tile .stat-val { color: var(--amber); }

/* ── Subject cards ── */
.subject-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(220px, 1fr)); gap: 1.2rem; }
.subject-card {
  border-radius: var(--radius);
  padding: 2rem 1.5rem;
  text-align: center;
  text-decoration: none;
  color: #fff;
  font-weight: 700;
  font-size: 1.15rem;
  box-shadow: var(--shadow);
  transition: transform .2s, filter .2s;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: .7rem;
}
.subject-card:hover { transform: translateY(-4px); filter: brightness(1.07); }
.subject-card .icon { font-size: 2.5rem; }
.bio-card  { background: linear-gradient(135deg,#2e7d32,#66bb6a); }
.chem-card { background: linear-gradient(135deg,#1565c0,#42a5f5); }
.phys-card { background: linear-gradient(135deg,#6a1b9a,#ab47bc); }
.mix-card  { background: linear-gradient(135deg,#e65100,#ffa726); }

/* ── Difficulty cards ── */
.diff-grid { display: grid; grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); gap: 1.2rem; }
.diff-card {
  border-radius: var(--radius);
  padding: 1.6rem 1.2rem;
  text-align: center;
  text-decoration: none;
  color: #fff;
  box-shadow: var(--shadow);
  transition: transform .2s;
}
.diff-card:hover { transform: translateY(-3px); }
.diff-card .diff-name { font-size: 1.1rem; font-weight: 700; }
.diff-card .diff-desc { font-size: .8rem; opacity: .85; margin-top: .5rem; }
.d1 { background: linear-gradient(135deg,#388e3c,#66bb6a); }
.d2 { background: linear-gradient(135deg,#0277bd,#29b6f6); }
.d3 { background: linear-gradient(135deg,#e65100,#ffa726); }
.d4 { background: linear-gradient(135deg,#b71c1c,#ef5350); }

/* ── Quiz ── */
.quiz-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1.2rem;
  flex-wrap: wrap;
  gap: .5rem;
}
.quiz-progress-bar {
  width: 100%;
  height: 8px;
  background: #e0e0e0;
  border-radius: 4px;
  margin-bottom: 1.5rem;
  overflow: hidden;
}
.quiz-progress-fill {
  height: 100%;
  background: var(--green-l);
  border-radius: 4px;
  transition: width .3s ease;
}
.question-card { display: none; }
.question-card.active { display: block; }
.question-text {
  font-size: 1.1rem;
  font-weight: 600;
  margin-bottom: 1.4rem;
  line-height: 1.6;
}
.options { display: flex; flex-direction: column; gap: .75rem; }
.option-btn {
  display: flex;
  align-items: center;
  gap: .9rem;
  padding: .85rem 1.1rem;
  border: 2px solid #cfd8dc;
  border-radius: 10px;
  background: var(--white);
  cursor: pointer;
  font-size: .97rem;
  text-align: left;
  transition: border-color .2s, background .2s;
}
.option-btn:hover { border-color: var(--green-l); background: var(--green-xl); }
.option-btn.selected { border-color: var(--green); background: var(--green-xl); }
.option-btn.selected .opt-letter { background: var(--green); color: #fff; }
.opt-letter {
  min-width: 32px;
  height: 32px;
  border-radius: 50%;
  background: #eceff1;
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  font-size: .85rem;
  transition: background .2s, color .2s;
}
.quiz-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-top: 1.5rem;
}
.question-counter { color: var(--grey); font-size: .9rem; }

/* ── Results ── */
.score-circle {
  width: 130px;
  height: 130px;
  border-radius: 50%;
  border: 8px solid var(--green-l);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  margin: 0 auto 1.5rem;
}
.score-circle.score-good  { border-color: var(--green-l); }
.score-circle.score-ok    { border-color: var(--amber); }
.score-circle.score-low   { border-color: var(--red); }
.score-pct {
  font-size: 2rem;
  font-weight: 800;
  line-height: 1;
  color: var(--green);
}
.score-circle.score-ok  .score-pct { color: var(--amber); }
.score-circle.score-low .score-pct { color: var(--red); }
.score-raw { font-size: .85rem; color: var(--grey); }

.xp-banner {
  background: var(--amber-xl);
  border-left: 4px solid var(--amber);
  border-radius: 8px;
  padding: .85rem 1.2rem;
  margin-bottom: 1rem;
  font-weight: 600;
  color: #5d4037;
}
.streak-banner {
  background: var(--green-xl);
  border-left: 4px solid var(--green-l);
  border-radius: 8px;
  padding: .85rem 1.2rem;
  margin-bottom: 1rem;
  font-weight: 600;
  color: var(--green);
}

.wrong-item {
  border: 1px solid #e0e0e0;
  border-radius: 10px;
  padding: 1.2rem;
  margin-bottom: 1rem;
  background: var(--red-xl);
  border-left: 4px solid var(--red);
}
.wrong-item .wq-text { font-weight: 600; margin-bottom: .7rem; }
.wrong-item .answer-row { display: flex; gap: .5rem; flex-wrap: wrap; margin-bottom: .4rem; }
.badge {
  display: inline-block;
  padding: .2rem .7rem;
  border-radius: 20px;
  font-size: .8rem;
  font-weight: 600;
}
.badge-wrong   { background: var(--red-xl);   color: var(--red); border: 1px solid var(--red); }
.badge-correct { background: var(--green-xl); color: var(--green); border: 1px solid var(--green); }
.explanation-box {
  background: #fff;
  border-radius: 8px;
  padding: .9rem;
  margin-top: .7rem;
  font-size: .9rem;
}
.explanation-box strong { color: var(--grey); }

/* ── History table ── */
table { width: 100%; border-collapse: collapse; font-size: .9rem; }
th { background: #eceff1; padding: .6rem .9rem; text-align: left; font-size: .8rem; text-transform: uppercase; letter-spacing: .04em; color: var(--grey); }
td { padding: .65rem .9rem; border-bottom: 1px solid #f0f0f0; }
tr:last-child td { border-bottom: none; }
tr:hover td { background: var(--light); }

/* ── Page headings ── */
.page-heading { font-size: 1.6rem; font-weight: 800; margin-bottom: .3rem; }
.page-sub     { color: var(--grey); font-size: .95rem; margin-bottom: 1.8rem; }

/* ── Auth page ── */
.auth-logo { text-align: center; margin-bottom: 1.5rem; }
.auth-logo .logo-icon { font-size: 3rem; }
.auth-logo h1 { font-size: 1.4rem; color: var(--green); font-weight: 800; }
.auth-logo p  { color: var(--grey); font-size: .9rem; }

/* ── Divider ── */
.divider { height: 1px; background: #e0e0e0; margin: 1.2rem 0; }

/* ── Pill badges ── */
.pill {
  display: inline-block;
  padding: .2rem .8rem;
  border-radius: 20px;
  font-size: .78rem;
  font-weight: 700;
}
.pill-bio  { background: #e8f5e9; color: #2e7d32; }
.pill-chem { background: #e3f2fd; color: #1565c0; }
.pill-phys { background: #f3e5f5; color: #6a1b9a; }
.pill-d1   { background: #e8f5e9; color: #2e7d32; }
.pill-d2   { background: #e3f2fd; color: #1565c0; }
.pill-d3   { background: #fff8e1; color: #e65100; }
.pill-d4   { background: #ffebee; color: #c62828; }

/* ── Responsive ── */
@media (max-width: 600px) {
  .stats-row { gap: .7rem; }
  .stat-tile { padding: .9rem; }
  .stat-tile .stat-val { font-size: 1.5rem; }
  .quiz-header { font-size: .85rem; }
  .question-text { font-size: 1rem; }
}

/* Topic grid */
.topic-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
  gap: 1rem;
  margin-top: 1.5rem;
}

.topic-card {
  display: block;
  background: #fff;
  border: 2px solid #e8f5e9;
  border-radius: 12px;
  padding: 1.2rem 1rem;
  text-decoration: none;
  color: #1b5e20;
  transition: border-color .2s, box-shadow .2s, transform .15s;
}

.topic-card:hover {
  border-color: #2e7d32;
  box-shadow: 0 4px 16px rgba(46,125,50,.15);
  transform: translateY(-2px);
}

.topic-card.topic-empty {
  opacity: .5;
  pointer-events: none;
}

.topic-code {
  font-size: 1.3rem;
  font-weight: 700;
  color: #2e7d32;
  margin-bottom: .25rem;
}

.topic-name {
  font-size: 1rem;
  font-weight: 600;
  color: #1b5e20;
  margin-bottom: .4rem;
}

.topic-count {
  font-size: .8rem;
  color: #546e7a;
}

/* Admin table responsive */
.admin-table-wrap {
  overflow-x: auto;
}