:root {
  --blue: #0b3d91;
  --blue-dark: #082a66;
  --gold: #ffb81c;
  --gold-dark: #d99400;
  --green: #157347;
  --green-soft: #e6f4ec;
  --red: #b02a37;
  --red-soft: #fbeaec;
  --ink: #1b2430;
  --muted: #5b6673;
  --line: #e3e7ec;
  --bg: #f4f6fa;
  --card: #ffffff;
  --shadow: 0 10px 30px rgba(11, 61, 145, 0.08);
  --radius: 14px;
}

* {
  box-sizing: border-box;
}

html,
body {
  margin: 0;
  padding: 0;
}

body {
  font-family:
    system-ui,
    -apple-system,
    'Segoe UI',
    Roboto,
    Helvetica,
    Arial,
    sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.5;
  -webkit-font-smoothing: antialiased;
}

.app {
  max-width: 760px;
  margin: 0 auto;
  padding: 20px 16px 48px;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

/* Header */
.app-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 20px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
}

.brand-badge {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 46px;
  height: 46px;
  border-radius: 12px;
  background: linear-gradient(135deg, var(--blue), var(--blue-dark));
  color: var(--gold);
  font-weight: 800;
  letter-spacing: 0.5px;
  font-size: 1.05rem;
  box-shadow: var(--shadow);
}

.brand-text h1 {
  margin: 0;
  font-size: 1.35rem;
  font-weight: 800;
  color: var(--blue);
}

.brand-text p {
  margin: 2px 0 0;
  font-size: 0.82rem;
  color: var(--muted);
}

.header-stats {
  text-align: right;
  font-size: 0.8rem;
  color: var(--muted);
  line-height: 1.3;
}

.header-stats strong {
  color: var(--blue);
  font-size: 1rem;
}

/* Screen + cards */
.screen {
  flex: 1;
}

.card {
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  box-shadow: var(--shadow);
  padding: 24px;
}

.app-footer {
  margin-top: 28px;
  text-align: center;
}

.app-footer p {
  font-size: 0.74rem;
  color: var(--muted);
  margin: 0;
}

/* Start screen */
.intro h2 {
  margin: 0 0 6px;
  font-size: 1.5rem;
}

.intro .lead {
  margin: 0 0 22px;
  color: var(--muted);
}

.mode {
  display: block;
  width: 100%;
  text-align: left;
  border: 2px solid var(--line);
  background: #fff;
  border-radius: 12px;
  padding: 18px 18px;
  margin-bottom: 14px;
  cursor: pointer;
  transition:
    border-color 0.15s ease,
    box-shadow 0.15s ease,
    transform 0.05s ease;
  font: inherit;
  color: inherit;
}

.mode:hover {
  border-color: var(--blue);
  box-shadow: var(--shadow);
}

.mode:active {
  transform: translateY(1px);
}

.mode .mode-title {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  font-size: 1.05rem;
}

.mode .mode-emoji {
  font-size: 1.3rem;
}

.mode .mode-desc {
  margin: 6px 0 0 34px;
  color: var(--muted);
  font-size: 0.9rem;
}

.panel {
  display: block;
  border: 2px solid var(--line);
  background: #fbfcfe;
  border-radius: 12px;
  padding: 18px;
  margin-bottom: 14px;
}

.panel .mode-title {
  display: flex;
  align-items: center;
  gap: 10px;
  font-weight: 700;
  font-size: 1.05rem;
}

.panel .mode-emoji {
  font-size: 1.3rem;
}

.panel .mode-desc {
  display: block;
  margin: 6px 0 0 34px;
  color: var(--muted);
  font-size: 0.9rem;
}

.field {
  margin-top: 18px;
}

.field label {
  display: block;
  font-size: 0.82rem;
  font-weight: 700;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.04em;
  margin-bottom: 8px;
}

select {
  width: 100%;
  font: inherit;
  padding: 12px 14px;
  border: 2px solid var(--line);
  border-radius: 10px;
  background: #fff;
  color: var(--ink);
  cursor: pointer;
  appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='16' height='16' viewBox='0 0 24 24' fill='none' stroke='%235b6673' stroke-width='2'%3E%3Cpath d='M6 9l6 6 6-6'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 14px center;
}

select:focus {
  outline: none;
  border-color: var(--blue);
}

/* Buttons */
.btn {
  font: inherit;
  font-weight: 700;
  border: none;
  border-radius: 10px;
  padding: 13px 20px;
  cursor: pointer;
  transition:
    background 0.15s ease,
    transform 0.05s ease,
    opacity 0.15s ease;
}

.btn:active {
  transform: translateY(1px);
}

.btn-primary {
  background: linear-gradient(135deg, var(--blue), var(--blue-dark));
  color: #fff;
}

.btn-primary:hover {
  background: var(--blue-dark);
}

.btn-gold {
  background: linear-gradient(135deg, var(--gold), var(--gold-dark));
  color: #3a2a00;
}

.btn-ghost {
  background: transparent;
  color: var(--blue);
  border: 2px solid var(--line);
}

.btn-ghost:hover {
  border-color: var(--blue);
}

.btn-block {
  display: block;
  width: 100%;
}

.btn:disabled {
  opacity: 0.55;
  cursor: default;
}

.btn-row {
  display: flex;
  gap: 10px;
  margin-top: 18px;
}

.btn-row .btn {
  flex: 1;
}

/* Quiz progress */
.quiz-top {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 14px;
}

.quiz-meta {
  font-size: 0.82rem;
  color: var(--muted);
  font-weight: 600;
}

.quiz-topic-tag {
  display: inline-block;
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--blue);
  background: #eaf0fb;
  border-radius: 999px;
  padding: 3px 10px;
}

.progress {
  height: 8px;
  background: #e9edf3;
  border-radius: 999px;
  overflow: hidden;
  margin-bottom: 20px;
}

.progress-bar {
  height: 100%;
  background: linear-gradient(90deg, var(--blue), var(--gold));
  border-radius: 999px;
  transition: width 0.3s ease;
}

.question {
  font-size: 1.22rem;
  font-weight: 600;
  margin: 0 0 20px;
}

/* Options */
.options {
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.option {
  display: flex;
  align-items: flex-start;
  gap: 12px;
  width: 100%;
  text-align: left;
  border: 2px solid var(--line);
  background: #fff;
  border-radius: 12px;
  padding: 14px 16px;
  cursor: pointer;
  font: inherit;
  color: inherit;
  transition:
    border-color 0.15s ease,
    background 0.15s ease;
}

.option:hover:not(:disabled) {
  border-color: var(--blue);
  background: #f7f9ff;
}

.option:disabled {
  cursor: default;
}

.option .key {
  flex-shrink: 0;
  width: 26px;
  height: 26px;
  border-radius: 7px;
  background: #eef1f6;
  color: var(--muted);
  font-weight: 700;
  font-size: 0.85rem;
  display: inline-flex;
  align-items: center;
  justify-content: center;
}

.option.correct {
  border-color: var(--green);
  background: var(--green-soft);
}

.option.correct .key {
  background: var(--green);
  color: #fff;
}

.option.incorrect {
  border-color: var(--red);
  background: var(--red-soft);
}

.option.incorrect .key {
  background: var(--red);
  color: #fff;
}

.option.chosen-review {
  box-shadow: 0 0 0 2px rgba(11, 61, 145, 0.15);
}

/* Feedback */
.feedback {
  margin-top: 18px;
  border-radius: 12px;
  padding: 14px 16px;
  font-size: 0.95rem;
}

.feedback.right {
  background: var(--green-soft);
  border: 1px solid #b7e0c6;
}

.feedback.wrong {
  background: var(--red-soft);
  border: 1px solid #eec2c7;
}

.feedback .verdict {
  font-weight: 800;
  display: block;
  margin-bottom: 4px;
}

.feedback.right .verdict {
  color: var(--green);
}

.feedback.wrong .verdict {
  color: var(--red);
}

.shake {
  animation: shake 0.4s ease-in-out;
}

@keyframes shake {
  0%,
  100% {
    transform: translateX(0);
  }
  20%,
  60% {
    transform: translateX(-6px);
  }
  40%,
  80% {
    transform: translateX(6px);
  }
}

/* Results */
.result-head {
  text-align: center;
  padding-bottom: 8px;
}

.result-badge {
  display: inline-block;
  font-weight: 800;
  font-size: 0.85rem;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  padding: 6px 16px;
  border-radius: 999px;
  margin-bottom: 12px;
}

.result-badge.pass {
  background: var(--green-soft);
  color: var(--green);
}

.result-badge.fail {
  background: var(--red-soft);
  color: var(--red);
}

.result-score {
  font-size: 3rem;
  font-weight: 800;
  color: var(--blue);
  line-height: 1;
}

.result-score span {
  font-size: 1.3rem;
  color: var(--muted);
}

.result-sub {
  color: var(--muted);
  margin-top: 8px;
}

.review-list {
  margin-top: 24px;
  display: flex;
  flex-direction: column;
  gap: 16px;
}

.review-item {
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 16px;
}

.review-item .rq {
  font-weight: 600;
  margin: 0 0 10px;
}

.review-item .ra {
  font-size: 0.9rem;
  margin: 4px 0;
}

.review-item .ra.ok {
  color: var(--green);
}

.review-item .ra.bad {
  color: var(--red);
}

.review-item .rexp {
  font-size: 0.88rem;
  color: var(--muted);
  margin-top: 8px;
}

.review-index {
  font-size: 0.72rem;
  font-weight: 700;
  color: var(--muted);
  text-transform: uppercase;
}

.explanation-source {
  font-size: 0.8rem;
  color: var(--muted);
  margin-top: 6px;
}

/* Small screens */
@media (max-width: 560px) {
  .brand-text h1 {
    font-size: 1.15rem;
  }
  .card {
    padding: 18px;
  }
  .question {
    font-size: 1.1rem;
  }
  .result-score {
    font-size: 2.4rem;
  }
}