:root {
  --navy:   #1a2456;
  --teal:   #1a9e72;
  --green:  #27ae60;
  --red:    #e74c3c;
  --bg:     #f0f2f5;
  --card:   #ffffff;
  --text:   #222222;
  --muted:  #777777;
  --border: #dde0e8;
}

/* ── Reset ── */
*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
body {
  font-family: 'Segoe UI', system-ui, -apple-system, sans-serif;
  background: var(--bg);
  color: var(--text);
  min-height: 100vh;
  font-size: 15px;
}

/* ── Screen management ── */
.screen { display: none; min-height: 100vh; }
.screen.active { display: block; }

/* ── Screen header ── */
.screen-header {
  background: var(--navy);
  color: #fff;
  padding: 18px 36px;
  font-size: 20px;
  font-weight: 700;
  letter-spacing: 0.2px;
}
.screen-num { font-weight: 900; }

/* ── Content wrapper ── */
.content {
  max-width: 920px;
  margin: 0 auto;
  padding: 36px 24px;
}
.content-center {
  max-width: 600px;
  text-align: center;
}

/* ── Question card ── */
.question-card {
  background: var(--card);
  border-radius: 8px;
  box-shadow: 0 1px 5px rgba(0,0,0,0.08);
  padding: 24px 28px;
  display: flex;
  gap: 20px;
  align-items: flex-start;
  margin-bottom: 24px;
}
.q-icon {
  width: 46px; height: 46px; flex-shrink: 0;
  background: var(--navy);
  color: #fff;
  border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  font-size: 24px; font-weight: 900;
}
.q-body { line-height: 1.75; color: var(--text); margin-bottom: 10px; }
.q-ask  { color: var(--navy); font-weight: 700; }

/* ── MCQ options ── */
.options-list { display: flex; flex-direction: column; gap: 12px; margin-bottom: 32px; }
.option-card {
  background: var(--card);
  border: 1.5px solid var(--border);
  border-radius: 6px;
  padding: 15px 22px;
  display: flex;
  align-items: center;
  gap: 16px;
  cursor: pointer;
  transition: border-color 0.15s, background 0.15s;
  user-select: none;
}
.option-card:hover { border-color: var(--navy); background: #f4f5ff; }
.option-card.selected { border-color: var(--navy); background: #eef0fb; }

.radio-outer {
  width: 22px; height: 22px; flex-shrink: 0;
  border: 2px solid #b0b5c8;
  border-radius: 50%;
  display: flex; align-items: center; justify-content: center;
  transition: border-color 0.15s;
}
.option-card.selected .radio-outer { border-color: var(--navy); }
.radio-inner {
  width: 12px; height: 12px;
  background: var(--navy);
  border-radius: 50%;
  display: none;
}
.option-card.selected .radio-inner { display: block; }
.opt-text { font-size: 15px; }

/* ── Buttons ── */
.btn-row { display: flex; justify-content: center; gap: 16px; flex-wrap: wrap; }

.btn-primary {
  padding: 14px 52px;
  background: var(--navy);
  color: #fff;
  border: none;
  border-radius: 4px;
  font-size: 14px;
  font-weight: 700;
  letter-spacing: 1.2px;
  cursor: pointer;
  transition: opacity 0.15s;
}
.btn-primary:hover { opacity: 0.88; }

.btn-teal {
  padding: 14px 44px;
  background: var(--teal);
  color: #fff;
  border: none;
  border-radius: 4px;
  font-size: 14px;
  font-weight: 700;
  letter-spacing: 1.2px;
  cursor: pointer;
  transition: opacity 0.15s;
}
.btn-teal:hover { opacity: 0.88; }

.btn-outline {
  padding: 12px 32px;
  background: transparent;
  color: var(--navy);
  border: 2px solid var(--navy);
  border-radius: 4px;
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  transition: background 0.15s, color 0.15s;
}
.btn-outline:hover { background: var(--navy); color: #fff; }

/* ── Feedback ── */
.feedback-row { display: flex; justify-content: center; margin-bottom: 36px; }
.feedback-card {
  background: var(--card);
  border-radius: 8px;
  box-shadow: 0 2px 12px rgba(0,0,0,0.10);
  padding: 44px 52px;
  text-align: center;
  max-width: 440px;
  width: 100%;
}
.feedback-card.correct-card  { border-top: 5px solid var(--green); }
.feedback-card.incorrect-card { border-top: 5px solid var(--red); }

.fb-icon {
  width: 72px; height: 72px;
  border-radius: 50%;
  margin: 0 auto 18px;
  display: flex; align-items: center; justify-content: center;
  font-size: 34px; color: #fff; font-weight: 900;
}
.icon-correct   { background: var(--green); }
.icon-incorrect { background: var(--red); }

.fb-title { font-size: 30px; font-weight: 700; margin-bottom: 14px; }
.fb-title.correct-color   { color: var(--green); }
.fb-title.incorrect-color { color: var(--red); }
.fb-option { font-size: 15px; color: #555; margin-bottom: 8px; }
.fb-sub { font-size: 14px; color: var(--muted); }

/* ── Explanation ── */
.explanation-card {
  background: var(--card);
  border-radius: 8px;
  box-shadow: 0 1px 5px rgba(0,0,0,0.07);
  padding: 22px 28px;
  line-height: 1.8;
  margin-bottom: 28px;
}
.expl-label { color: var(--navy); font-weight: 700; font-size: 15px; }

/* ── Graphs row ── */
.graphs-row {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 20px;
  margin-bottom: 28px;
}
.graph-box {
  background: var(--card);
  border-radius: 8px;
  box-shadow: 0 1px 5px rgba(0,0,0,0.07);
  padding: 14px;
  overflow: hidden;
}
.graph-box canvas { display: block; width: 100%; height: 300px; }

/* ── Explore card ── */
.explore-card {
  background: #eef0fb;
  border: 1.5px solid #cdd1ee;
  border-radius: 8px;
  padding: 22px 28px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 24px;
}
.explore-title { font-weight: 700; font-size: 15px; color: var(--navy); margin-bottom: 4px; }
.explore-sub { font-size: 13px; color: var(--muted); }

/* ── Custom input ── */
.keyboard-icon { font-size: 54px; margin-bottom: 14px; }
.input-title { font-size: 30px; font-weight: 700; color: var(--navy); margin-bottom: 30px; }

.input-form { text-align: left; margin-bottom: 32px; display: flex; flex-direction: column; gap: 14px; }
.input-group {
  background: var(--card);
  border-radius: 8px;
  box-shadow: 0 1px 4px rgba(0,0,0,0.07);
  padding: 16px 22px;
}
.input-label { display: block; font-weight: 700; color: var(--navy); font-size: 13.5px; margin-bottom: 9px; }
.text-input {
  width: 100%; border: none;
  background: #f4f6fa; border-radius: 4px;
  padding: 11px 16px; font-size: 15px;
  color: #444; outline: none; font-family: inherit;
  transition: background 0.15s;
}
.text-input:focus { background: #eaecf8; }
.text-input::placeholder { color: #bbb; font-style: italic; }

/* ── Values summary banner ── */
.values-summary {
  background: #eef0fb;
  border: 1.5px solid #cdd1ee;
  border-radius: 8px;
  padding: 18px 28px;
  text-align: center;
  font-size: 16px;
  font-weight: 700;
  color: var(--navy);
  margin-bottom: 28px;
  letter-spacing: 0.3px;
}

/* ── Observation card ── */
.observation-card {
  background: var(--card);
  border-radius: 8px;
  box-shadow: 0 1px 5px rgba(0,0,0,0.07);
  padding: 20px 26px;
  display: flex;
  align-items: flex-start;
  gap: 16px;
  line-height: 1.75;
  margin-top: 4px;
}
.obs-icon { font-size: 30px; flex-shrink: 0; margin-top: 2px; }
.obs-label { font-weight: 700; color: var(--navy); }

/* ── Error message ── */
.error-msg {
  color: var(--red);
  font-size: 13px;
  margin-top: 10px;
  text-align: center;
  min-height: 20px;
}

/* ── Responsive ── */
@media (max-width: 680px) {
  .graphs-row { grid-template-columns: 1fr; }
  .explore-card { flex-direction: column; align-items: flex-start; }
  .screen-header { padding: 16px 20px; font-size: 16px; }
  .content { padding: 24px 16px; }
  .feedback-card { padding: 32px 24px; }
}