:root {
  --dark: #111827;
  --dark-btn: #1a1a2e;
  --white: #ffffff;
  --bg: #f9fafb;
  --border: #e5e7eb;
  --text: #111827;
  --muted: #6b7280;
  --answer-bg: #f3f4f6;
  --green: #16a34a;
  --red: #dc2626;
  --yellow: #d97706;
  --radius: 12px;
  --radius-sm: 8px;
}

* { box-sizing: border-box; margin: 0; padding: 0; -webkit-tap-highlight-color: transparent; }

html, body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background: var(--bg);
  color: var(--text);
  font-size: 16px;
  transition: background 0.3s;
}
body.op-add  { background: #D1FAE5; }
body.op-sub  { background: #FFE4E4; }
body.op-mul  { background: #FFEDD5; }
body.op-div  { background: #FEFCE8; }
body.op-frac { background: #DBEAFE; }

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

/* HOME */
.home-wrap {
  min-height: 100vh;
  padding: 40px 32px 60px;
  max-width: 860px;
  margin: 0 auto;
  display: flex;
  flex-direction: column;
  gap: 28px;
}
.home-header { text-align: center; padding: 8px 0 4px; }
.home-title {
  font-size: 52px;
  font-weight: 800;
  color: var(--text);
  letter-spacing: -1px;
}
.title-noku { color: #6EE7B7; font-weight: 800; }
.title-dot  { color: #111827; font-weight: 800; }
.title-ai   { color: #6EE7B7; font-weight: 800; }
.home-sub { font-size: 17px; color: var(--muted); margin-top: 6px; }

.home-label {
  font-size: 14px;
  font-weight: 600;
  color: var(--muted);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  margin-bottom: 12px;
  text-align: center;
}
.home-section { display: flex; flex-direction: column; align-items: center; }
.home-section .option-group { justify-content: center; }

/* Operation cards */
.home-op-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 12px;
}
.home-op-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 8px;
  padding: 20px 12px;
  border-radius: var(--radius);
  border: 2.5px solid transparent;
  cursor: pointer;
  transition: all 0.15s;
  touch-action: manipulation;
}
.home-op-btn.op-add  { background: #D1FAE5; border-color: #A7F3D0; }
.home-op-btn.op-sub  { background: #FFE4E4; border-color: #FCA5A5; }
.home-op-btn.op-mul  { background: #FFEDD5; border-color: #FDBA74; }
.home-op-btn.op-div  { background: #FEFCE8; border-color: #FDE047; }
.home-op-btn.op-frac { background: #DBEAFE; border-color: #93C5FD; }

.home-op-btn:hover { transform: translateY(-2px); box-shadow: 0 4px 16px rgba(0,0,0,0.1); }
.home-op-btn.active { border-width: 3px; box-shadow: 0 4px 20px rgba(0,0,0,0.15); transform: translateY(-2px); }
.home-op-btn.op-add.active  { border-color: #34d399; }
.home-op-btn.op-sub.active  { border-color: #f87171; }
.home-op-btn.op-mul.active  { border-color: #fb923c; }
.home-op-btn.op-div.active  { border-color: #facc15; }
.home-op-btn.op-frac.active { border-color: #60a5fa; }

.hop-icon {
  font-size: 32px;
  font-weight: 800;
  line-height: 1;
  color: var(--text);
}
.hop-name { font-size: 13px; font-weight: 600; color: var(--text); }

.home-start { align-items: center; gap: 12px; }
input.home-name-input {
  width: 100%;
  max-width: 360px;
  padding: 15px 18px;
  border: 2px solid #F9A8D4 !important;
  border-radius: var(--radius-sm);
  font-size: 18px;
  background: #FCE7F3 !important;
  color: #831843;
  outline: none;
  text-align: center;
}
input.home-name-input:focus { border-color: #ec4899 !important; }
input.home-name-input::placeholder { color: #F9A8D4; }
.btn-dark.home-start-btn { max-width: 360px; font-size: 18px; padding: 18px 32px; background: #DBEAFE; color: #1e3a6e; border: 2px solid #93C5FD; }
.btn-dark.home-start-btn:hover { background: #BFDBFE; opacity: 1; }

/* keep old login card for fallback */
.login-wrap {
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  min-height: 100vh;
  padding: 24px;
}
.login-card {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 32px 28px;
  width: 100%;
  max-width: 400px;
  display: flex;
  flex-direction: column;
  gap: 14px;
  margin-top: 24px;
}

/* TYPOGRAPHY */
.app-title {
  font-size: 28px;
  font-weight: 700;
  color: var(--text);
  text-align: center;
}
.app-sub {
  font-size: 15px;
  color: var(--muted);
  text-align: center;
  margin-top: 6px;
}

/* PAGE LAYOUT */
.page-top {
  background: var(--white);
  border-bottom: 1px solid var(--border);
  padding: 24px 32px 0;
  max-width: 1400px;
  margin: 0 auto;
}
.page-title-row {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 16px;
  margin-bottom: 20px;
}
.page-title-row .app-title { text-align: left; }
.page-title-row .app-sub { text-align: left; }

.top-actions { display: flex; align-items: center; gap: 8px; flex-wrap: wrap; }
.student-badge {
  background: var(--answer-bg);
  border-radius: 20px;
  padding: 6px 14px;
  font-size: 14px;
  font-weight: 600;
  color: var(--muted);
}

/* SETTINGS CARD */
.settings-card {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius) var(--radius) 0 0;
  padding: 24px 28px;
  display: flex;
  flex-direction: column;
  gap: 20px;
}
.setting-row {
  display: flex;
  align-items: center;
  gap: 20px;
  flex-wrap: wrap;
}
.setting-label {
  font-size: 15px;
  font-weight: 600;
  color: var(--text);
  white-space: nowrap;
  min-width: 180px;
}
.option-group { display: flex; gap: 10px; flex-wrap: wrap; }

/* OPTION BUTTONS */
.opt-btn {
  padding: 10px 18px;
  border-radius: var(--radius-sm);
  border: 1.5px solid var(--border);
  background: var(--white);
  font-size: 15px;
  font-weight: 500;
  color: var(--text);
  cursor: pointer;
  transition: all 0.15s;
  touch-action: manipulation;
  min-height: 44px;
}
.opt-btn:hover { border-color: var(--dark); }
.opt-btn.active { background: var(--dark); color: var(--white); border-color: var(--dark); }
.opt-btn.op-add.active  { background: #A8F5D1; color: #1a5c3a; border-color: #A8F5D1; }
.opt-btn.op-sub.active  { background: #FF9494; color: #7a0000; border-color: #FF9494; }
.opt-btn.op-mul.active  { background: #FFB87A; color: #7a3800; border-color: #FFB87A; }
.opt-btn.op-div.active  { background: #FFF176; color: #5a4a00; border-color: #FFF176; }
.opt-btn.op-frac.active { background: #93C5FD; color: #1e3a6e; border-color: #93C5FD; }

/* Difficulty pastel colors */
.diff-btn[data-val="easy"]   { background: #D1FAE5; border-color: #6EE7B7; color: #065f46; }
.diff-btn[data-val="medium"] { background: #FFEDD5; border-color: #FDBA74; color: #7c2d12; }
.diff-btn[data-val="hard"]   { background: #DBEAFE; border-color: #93C5FD; color: #1e3a6e; }
.diff-btn[data-val="easy"].active   { background: #6EE7B7; border-color: #34d399; color: #064e3b; box-shadow: 0 2px 10px rgba(52,211,153,0.4); }
.diff-btn[data-val="medium"].active { background: #FDBA74; border-color: #fb923c; color: #7c2d12; box-shadow: 0 2px 10px rgba(251,146,60,0.4); }
.diff-btn[data-val="hard"].active   { background: #93C5FD; border-color: #60a5fa; color: #1e3a6e; box-shadow: 0 2px 10px rgba(96,165,250,0.4); }

/* Count pastel colors */
.count-btn[data-val="25"]  { background: #D1FAE5; border-color: #6EE7B7; color: #065f46; }
.count-btn[data-val="50"]  { background: #FCE7F3; border-color: #F9A8D4; color: #831843; }
.count-btn[data-val="75"]  { background: #FFEDD5; border-color: #FDBA74; color: #7c2d12; }
.count-btn[data-val="100"] { background: #FEFCE8; border-color: #FDE047; color: #713f12; }
.count-btn[data-val="25"].active  { background: #6EE7B7; border-color: #34d399; color: #064e3b; box-shadow: 0 2px 10px rgba(52,211,153,0.4); }
.count-btn[data-val="50"].active  { background: #F9A8D4; border-color: #ec4899; color: #831843; box-shadow: 0 2px 10px rgba(236,72,153,0.3); }
.count-btn[data-val="75"].active  { background: #FDBA74; border-color: #fb923c; color: #7c2d12; box-shadow: 0 2px 10px rgba(251,146,60,0.4); }
.count-btn[data-val="100"].active { background: #FDE047; border-color: #eab308; color: #713f12; box-shadow: 0 2px 10px rgba(234,179,8,0.4); }

.diff-btn {
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 12px 24px;
  gap: 2px;
}
.diff-btn span { font-size: 16px; font-weight: 600; }
.diff-btn small { font-size: 12px; opacity: 0.7; }
.diff-btn.active small { opacity: 0.8; }

.count-btn {
  padding: 10px 20px;
  font-size: 16px;
  font-weight: 600;
  min-width: 60px;
  text-align: center;
}

.ws-info {
  font-size: 14px;
  color: var(--muted);
  font-weight: 500;
  padding: 10px 0 16px;
}

/* PROBLEMS GRID */
.problems-grid {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
}
.problems-grid.frac-grid {
  grid-template-columns: repeat(5, 1fr);
}

.problem-card {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 16px 16px;
  display: flex;
  flex-direction: column;
}
.op-add .problem-card  { background: #F0FDF7; border: 3px solid #6EE7B7; }
.op-sub .problem-card  { background: #FFF5F5; border: 3px solid #FCA5A5; }
.op-mul .problem-card  { background: #FFF8F0; border: 3px solid #FDBA74; }
.op-div .problem-card  { background: #FEFEF0; border: 3px solid #FDE047; }
.op-frac .problem-card { background: #F0F7FF; border: 3px solid #93C5FD; }
.problem-card.correct { border-color: var(--green); }
.problem-card.wrong { border-color: var(--red); }

.prob-numbers {
  text-align: right;
  line-height: 1.2;
  margin-bottom: 10px;
}
.prob-a {
  font-size: 32px;
  font-weight: 700;
  display: block;
  color: var(--text);
}
.prob-b {
  font-size: 32px;
  font-weight: 700;
  display: block;
  color: var(--text);
}
.prob-b .op {
  margin-right: 6px;
  font-weight: 400;
}
.prob-line {
  border: none;
  border-top: 2px solid var(--text);
  margin-bottom: 10px;
  width: 100%;
}

/* ANSWER INPUT — large for stylus writing */
.answer-input {
  background: rgba(255,255,255,0.75);
  border: none;
  border-radius: var(--radius-sm);
  width: 100%;
  padding: 14px 10px;
  font-size: 24px;
  font-weight: 700;
  text-align: center;
  color: var(--text);
  outline: none;
  cursor: text;
  min-height: 56px;
  /* optimized for Apple Pencil Scribble */
  -webkit-user-select: text;
  user-select: text;
}
.answer-input::placeholder { color: #c0c4cc; font-weight: 400; font-size: 20px; }
.answer-input:focus { background: #ebebf0; }
.answer-input.correct-ans { background: #dcfce7; color: var(--green); }
.answer-input.wrong-ans { background: #fee2e2; color: var(--red); }

/* FRACTION CARDS */
.frac-card {
  padding: 12px 8px;
}
.frac-equation {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 4px;
  flex-wrap: nowrap;
}
.frac-display {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  font-size: 17px;
  font-weight: 700;
  line-height: 1.1;
}
.frac-n, .frac-d { display: block; text-align: center; min-width: 18px; }
.frac-bar-h {
  width: 100%;
  border-top: 2px solid var(--text);
  display: block;
  min-width: 20px;
}
.frac-op, .frac-eq {
  font-size: 16px;
  font-weight: 600;
  color: var(--text);
  padding: 0 1px;
}
.frac-answer {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
}
.frac-input {
  width: 34px;
  height: 28px;
  background: var(--answer-bg);
  border: none;
  border-radius: 5px;
  font-size: 15px;
  font-weight: 700;
  text-align: center;
  color: var(--text);
  outline: none;
  -webkit-user-select: text;
  user-select: text;
}
.frac-input::placeholder { color: #c0c4cc; font-size: 13px; }
.frac-input:focus { background: #ebebf0; }
.frac-input.correct-ans { background: #dcfce7; color: var(--green); }
.frac-input.wrong-ans { background: #fee2e2; color: var(--red); }
.frac-bar-ans {
  width: 34px;
  border-top: 2px solid var(--text);
  display: block;
}

.result-badge {
  display: flex;
  align-items: center;
  justify-content: space-between;
  margin-top: 8px;
  font-size: 13px;
  font-weight: 600;
  min-height: 18px;
}
.result-badge .correct-label { color: var(--green); }
.result-badge .wrong-label { color: var(--red); }
.result-badge .correct-val { color: var(--green); }

/* SUBMIT ROW */
.submit-row {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 14px;
  padding: 0 32px 48px;
  max-width: 1400px;
  margin: 0 auto;
}

/* INPUTS */
input[type="text"], input[type="password"] {
  width: 100%;
  padding: 15px 16px;
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  font-size: 17px;
  background: var(--bg);
  color: var(--text);
  outline: none;
}
input:focus { border-color: var(--dark); }

/* BUTTONS */
.btn-dark {
  background: var(--dark);
  color: var(--white);
  border: none;
  border-radius: var(--radius-sm);
  padding: 14px 28px;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  min-height: 50px;
  touch-action: manipulation;
  transition: opacity 0.15s;
}
.btn-dark:hover { opacity: 0.85; }
.btn-dark:active { opacity: 0.7; }
.btn-full { width: 100%; }
.btn-submit { min-width: 220px; }

.btn-outline {
  background: transparent;
  color: var(--text);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 14px 28px;
  font-size: 16px;
  font-weight: 600;
  cursor: pointer;
  min-height: 50px;
  touch-action: manipulation;
}
.btn-outline:hover { border-color: var(--dark); }

.btn-outline-sm {
  background: #f3f4f6;
  color: var(--text);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 8px 16px;
  font-size: 14px;
  font-weight: 700;
  cursor: pointer;
  min-height: 38px;
  touch-action: manipulation;
  white-space: nowrap;
  transition: all 0.15s;
}
.btn-outline-sm:hover { filter: brightness(0.93); }

/* Nav button colors */
.btn-home     { background: #D1FAE5; border-color: #6EE7B7; color: #065f46; }
.btn-progress { background: #DBEAFE; border-color: #93C5FD; color: #1e3a6e; }
.btn-workbook { background: #FFEDD5; border-color: #FDBA74; color: #7c2d12; }
.btn-logout   { background: #FFE4E4; border-color: #FCA5A5; color: #7f1d1d; }

.btn-ghost {
  background: #FFEDD5;
  border: 2px solid #FDBA74;
  border-radius: var(--radius-sm);
  color: #7c2d12;
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  padding: 10px 24px;
  text-align: center;
  touch-action: manipulation;
  transition: all 0.15s;
}
.btn-ghost:hover { background: #FED7AA; }

/* RESULTS */
.results-wrap {
  max-width: 700px;
  margin: 0 auto;
  padding: 32px;
}
.score-card {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 36px;
  text-align: center;
  margin-bottom: 24px;
}
.res-emoji { font-size: 56px; margin-bottom: 12px; }
.res-score { font-size: 52px; font-weight: 800; color: var(--text); }
.res-pct { font-size: 22px; color: var(--muted); margin-bottom: 8px; }
.res-msg { font-size: 20px; font-weight: 600; }

.res-review {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px 24px;
  margin-bottom: 24px;
  display: flex;
  flex-direction: column;
  gap: 10px;
}
.rev-row {
  display: flex;
  align-items: center;
  gap: 12px;
  font-size: 16px;
}
.rev-icon { font-size: 18px; width: 24px; }
.rev-problem { font-weight: 600; flex: 1; }
.rev-answer { color: var(--muted); }
.rev-correct { color: var(--red); font-weight: 600; }
.res-actions { display: flex; gap: 12px; }

/* PROGRESS */
.inner-wrap { max-width: 900px; margin: 0 auto; padding: 28px 32px; }
.tabs { display: flex; gap: 8px; margin-bottom: 20px; flex-wrap: wrap; }
.tab {
  padding: 10px 20px;
  border-radius: 20px;
  border: 1.5px solid var(--border);
  background: var(--white);
  font-size: 15px;
  font-weight: 600;
  cursor: pointer;
  color: var(--muted);
  transition: all 0.15s;
}
.tab.active { background: var(--dark); border-color: var(--dark); color: var(--white); }

.mastery-summary { font-size: 15px; color: var(--muted); margin-bottom: 16px; }
.mastery-board {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(80px, 1fr));
  gap: 8px;
  margin-bottom: 20px;
}
.fact-cell {
  background: var(--white);
  border: 1.5px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 10px 6px;
  text-align: center;
  font-size: 13px;
  font-weight: 600;
}
.fact-cell.mastered { background: #f0fdf4; border-color: #86efac; color: #166534; }
.fact-cell.learning { background: #fffbeb; border-color: #fcd34d; color: #92400e; }
.fact-cell.weak { background: #fef2f2; border-color: #fca5a5; color: #991b1b; }

.legend { display: flex; gap: 20px; flex-wrap: wrap; font-size: 13px; color: var(--muted); }
.dot { display: inline-block; width: 10px; height: 10px; border-radius: 50%; margin-right: 5px; vertical-align: middle; }
.dot.green { background: var(--green); }
.dot.yellow { background: var(--yellow); }
.dot.red { background: var(--red); }
.dot.gray { background: var(--border); }

/* WORKBOOK */
.workbook-list { display: flex; flex-direction: column; gap: 12px; }
.wb-card {
  background: var(--white);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 16px 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
}
.wb-title { font-size: 16px; font-weight: 600; }
.wb-meta { font-size: 13px; color: var(--muted); margin-top: 3px; }
.wb-pct { font-size: 24px; font-weight: 800; color: var(--text); }
.wb-pct.high { color: var(--green); }
.wb-pct.mid { color: var(--yellow); }
.wb-pct.low { color: var(--red); }
.empty-state { text-align: center; padding: 60px 20px; color: var(--muted); }
.empty-icon { font-size: 40px; display: block; margin-bottom: 12px; }

/* PRINT */
@media print {
  .page-top, .top-actions, .submit-row, .btn-dark, .btn-outline, .btn-outline-sm { display: none !important; }
  .problems-grid { padding: 0; }
  .problem-card { break-inside: avoid; border: 1px solid #ccc; }
  .answer-input { background: white; border: none; border-radius: 0; }
}

/* HOME RESPONSIVE */
@media (max-width: 768px) {
  .home-wrap { padding: 28px 20px 48px; gap: 20px; }
  .home-title { font-size: 40px; }
  .home-op-grid { grid-template-columns: repeat(5, 1fr); }
  .home-row { flex-direction: column; }
}

/* RESPONSIVE — iPad portrait */
@media (max-width: 1024px) {
  .problems-grid { grid-template-columns: repeat(5, 1fr); padding: 20px 24px; }
  .page-top { padding: 20px 24px 0; }
}
@media (max-width: 768px) {
  .problems-grid { grid-template-columns: repeat(5, 1fr); padding: 12px; gap: 8px; }
  .setting-row { flex-direction: column; align-items: flex-start; gap: 10px; }
  .setting-label { min-width: unset; }
  .page-top { padding: 12px 12px 0; }
  .app-title { font-size: 16px; }
  .app-sub { display: none; }
  .page-title-row { flex-direction: row; align-items: center; gap: 8px; }
  .page-top { padding: 8px 12px 0; }
  .top-actions { gap: 4px; }
  .btn-outline-sm { padding: 6px 10px; font-size: 12px; }
  .submit-row { padding: 0 12px 40px; flex-direction: column; }
  .btn-submit { width: 100%; }
  .prob-a, .prob-b { font-size: 24px; }
  .answer-input { font-size: 20px; padding: 10px 6px; }
  .problem-card { align-items: center; }
  .prob-numbers { display: inline-block; text-align: right; }
  .prob-line { width: 100%; }
}
@media (max-width: 480px) {
  .problems-grid { grid-template-columns: repeat(3, 1fr); }
}