/* ═══════════════════════════════════════════════
   Final Grade Calculator — RogerHub Style CSS
   ═══════════════════════════════════════════════ */

:root {
  --bg-dark:    #1b2b36;
  --bg-card:    #243545;
  --bg-input:   #1a2e3d;
  --accent:     #4a9fd4;
  --accent-hover: #3a8fc4;
  --text-light: #e8f0f5;
  --text-muted: #8ca7bb;
  --border:     #2e4a5f;
  --success:    #27ae60;
  --warning:    #f39c12;
  --danger:     #e74c3c;
  --radius:     8px;
}

* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  background-color: var(--bg-dark);
  color: var(--text-light);
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  font-size: 16px;
  line-height: 1.6;
  min-height: 100vh;
}

/* ── HEADER ────────────────────────────────── */
header {
  background-color: #0f1e28;
  border-bottom: 2px solid var(--accent);
  padding: 16px 0;
}

header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

header h1 {
  font-size: 1.6rem;
  color: var(--accent);
  font-weight: 700;
  letter-spacing: 1px;
}

header h1 span {
  color: var(--text-light);
  font-weight: 300;
}

nav a {
  color: var(--text-muted);
  text-decoration: none;
  margin-left: 20px;
  font-size: 0.9rem;
  transition: color 0.2s;
}

nav a:hover { color: var(--accent); }

/* ── CONTAINER ──────────────────────────────── */
.container {
  max-width: 860px;
  margin: 0 auto;
  padding: 0 20px;
}

/* ── HERO ────────────────────────────────────── */
.hero {
  text-align: center;
  padding: 40px 0 20px;
}

.hero h2 {
  font-size: 2rem;
  color: var(--text-light);
  margin-bottom: 10px;
}

.hero p {
  color: var(--text-muted);
  font-size: 1rem;
  max-width: 600px;
  margin: 0 auto;
}

/* ── MODE TABS ───────────────────────────────── */
.mode-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin: 30px 0 20px;
  border-bottom: 1px solid var(--border);
  padding-bottom: 16px;
}

.mode-tab {
  background: var(--bg-card);
  color: var(--text-muted);
  border: 1px solid var(--border);
  padding: 8px 16px;
  border-radius: 20px;
  font-size: 0.85rem;
  cursor: pointer;
  transition: all 0.2s;
  text-decoration: none;
}

.mode-tab:hover,
.mode-tab.active {
  background: var(--accent);
  color: white;
  border-color: var(--accent);
}

/* ── CARD ──────────────────────────────────── */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 30px;
  margin-bottom: 24px;
}

.card h3 {
  font-size: 1.2rem;
  color: var(--accent);
  margin-bottom: 8px;
  display: flex;
  align-items: center;
  gap: 8px;
}

.card p.description {
  color: var(--text-muted);
  font-size: 0.9rem;
  margin-bottom: 24px;
  padding-bottom: 16px;
  border-bottom: 1px solid var(--border);
}

/* ── FORM ──────────────────────────────────── */
.form-group {
  margin-bottom: 18px;
}

.form-group label {
  display: block;
  color: var(--text-muted);
  font-size: 0.9rem;
  margin-bottom: 6px;
}

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

.form-row span {
  color: var(--text-muted);
  font-size: 0.95rem;
  white-space: nowrap;
}

input[type="number"],
input[type="text"] {
  background: var(--bg-input);
  border: 1px solid var(--border);
  color: var(--text-light);
  padding: 10px 14px;
  border-radius: var(--radius);
  font-size: 1rem;
  width: 120px;
  transition: border-color 0.2s, box-shadow 0.2s;
  -moz-appearance: textfield;
}

input[type="number"]::-webkit-outer-spin-button,
input[type="number"]::-webkit-inner-spin-button {
  -webkit-appearance: none;
  margin: 0;
}

input[type="number"]:focus,
input[type="text"]:focus {
  outline: none;
  border-color: var(--accent);
  box-shadow: 0 0 0 3px rgba(74, 159, 212, 0.2);
}

input.wide { width: 180px; }

/* ── BUTTON ──────────────────────────────────── */
.btn {
  background: var(--accent);
  color: white;
  border: none;
  padding: 12px 28px;
  border-radius: var(--radius);
  font-size: 1rem;
  cursor: pointer;
  font-weight: 600;
  transition: background 0.2s, transform 0.1s;
  margin-top: 10px;
}

.btn:hover {
  background: var(--accent-hover);
}

.btn:active {
  transform: scale(0.98);
}

/* ── RESULT BOX ─────────────────────────────── */
.result-box {
  margin-top: 24px;
  border-radius: var(--radius);
  overflow: hidden;
  animation: slideIn 0.3s ease;
}

@keyframes slideIn {
  from { opacity: 0; transform: translateY(-10px); }
  to   { opacity: 1; transform: translateY(0); }
}

.result-header {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: 20px 24px;
}

.result-score {
  font-size: 3rem;
  font-weight: 800;
  line-height: 1;
}

.result-label {
  font-size: 0.9rem;
  opacity: 0.8;
  margin-top: 4px;
}

.result-letter {
  font-size: 4rem;
  font-weight: 900;
  opacity: 0.3;
}

.result-body {
  padding: 16px 24px 20px;
  background: rgba(0,0,0,0.15);
}

.result-message {
  font-size: 1rem;
  margin-bottom: 12px;
}

.result-formula {
  font-family: 'Courier New', monospace;
  font-size: 0.82rem;
  opacity: 0.7;
  background: rgba(0,0,0,0.2);
  padding: 8px 12px;
  border-radius: 4px;
  word-break: break-all;
}

/* Grade color themes */
.grade-a         { background: linear-gradient(135deg, #1a5c35, #27ae60); color: white; }
.grade-b         { background: linear-gradient(135deg, #1a4a6e, #2980b9); color: white; }
.grade-c         { background: linear-gradient(135deg, #5a4a00, #f39c12); color: white; }
.grade-d         { background: linear-gradient(135deg, #5a2d00, #e67e22); color: white; }
.grade-f         { background: linear-gradient(135deg, #4a0a0a, #c0392b); color: white; }
.grade-impossible{ background: linear-gradient(135deg, #2d1515, #7f1d1d);  color: #fca5a5; }  /* dark red — not achievable */
.grade-already   { background: linear-gradient(135deg, #0a3d1f, #16a34a);  color: #bbf7d0; }  /* bright green — already done */

/* Error box */
.error-box {
  background: rgba(231, 76, 60, 0.15);
  border: 1px solid var(--danger);
  border-radius: var(--radius);
  padding: 14px 18px;
  color: #ff8a80;
  margin-top: 16px;
  display: flex;
  align-items: center;
  gap: 10px;
}

/* ── FORMULA SECTION ─────────────────────────── */
.how-it-works {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 28px 30px;
  margin-bottom: 24px;
}

.how-it-works h3 {
  color: var(--accent);
  margin-bottom: 14px;
  font-size: 1.1rem;
}

.how-it-works p {
  color: var(--text-muted);
  font-size: 0.92rem;
  margin-bottom: 12px;
}

.formula-display {
  background: rgba(0,0,0,0.3);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 20px;
  font-family: 'Courier New', monospace;
  font-size: 0.95rem;
  color: #7dd3fc;
  text-align: center;
  margin: 16px 0;
}

/* ── DYNAMIC FIELDS ──────────────────────────── */
.dynamic-fields {
  border-top: 1px dashed var(--border);
  padding-top: 18px;
  margin-top: 4px;
}

.dynamic-fields .form-group {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 10px;
}

.dynamic-fields label {
  min-width: 120px;
  margin-bottom: 0;
}

/* ── FOOTER ──────────────────────────────────── */
footer {
  text-align: center;
  padding: 30px 20px;
  color: var(--text-muted);
  font-size: 0.85rem;
  border-top: 1px solid var(--border);
  margin-top: 40px;
}

footer a {
  color: var(--accent);
  text-decoration: none;
}

/* ── RESPONSIVE ──────────────────────────────── */
@media (max-width: 600px) {
  .hero h2     { font-size: 1.5rem; }
  .result-score { font-size: 2.2rem; }
  .result-letter { font-size: 3rem; }
  .form-row    { flex-wrap: wrap; }
  input[type="number"] { width: 100px; }
  .card        { padding: 20px; }
  header .container { flex-direction: column; gap: 10px; }
  .mode-tabs   { gap: 6px; }
  .mode-tab    { padding: 6px 12px; font-size: 0.8rem; }
}

/* ── ADVANCED MODE ───────────────────────────────── */
.adv-category-row {
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 16px 18px;
  margin-bottom: 12px;
  position: relative;
}

.adv-category-row .cat-header {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 12px;
}

.adv-category-row .cat-header input[type="text"] {
  width: 160px;
  font-weight: 600;
  color: var(--accent);
}

.adv-category-row .cat-header .weight-input {
  width: 70px;
}

.adv-fields-grid {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px 20px;
}

.adv-fields-grid .form-group {
  margin-bottom: 0;
}

.adv-fields-grid label {
  font-size: 0.8rem;
}

.adv-fields-grid input {
  width: 100%;
}

.btn-add-cat {
  background: transparent;
  border: 1px dashed var(--accent);
  color: var(--accent);
  padding: 10px 20px;
  border-radius: var(--radius);
  cursor: pointer;
  font-size: 0.9rem;
  width: 100%;
  margin-bottom: 16px;
  transition: background 0.2s;
}
.btn-add-cat:hover { background: rgba(74,159,212,0.1); }

.btn-remove-cat {
  position: absolute;
  top: 10px;
  right: 12px;
  background: transparent;
  border: none;
  color: var(--text-muted);
  cursor: pointer;
  font-size: 1.1rem;
  line-height: 1;
}
.btn-remove-cat:hover { color: var(--danger); }

.weight-counter {
  background: var(--bg-input);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 10px 16px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 16px;
  font-size: 0.9rem;
}

.weight-counter span { color: var(--text-muted); }
.weight-counter strong { color: var(--accent); font-size: 1.1rem; }
.weight-counter.over  strong { color: var(--danger); }
.weight-counter.exact strong { color: var(--success); }

.adv-final-section {
  border-top: 2px dashed var(--accent);
  padding-top: 18px;
  margin-top: 6px;
}

.adv-final-section h4 {
  color: var(--accent);
  margin-bottom: 14px;
  font-size: 1rem;
}

.advanced-tip {
  background: rgba(74, 159, 212, 0.08);
  border-left: 3px solid var(--accent);
  padding: 10px 14px;
  border-radius: 0 var(--radius) var(--radius) 0;
  font-size: 0.83rem;
  color: var(--text-muted);
  margin-bottom: 20px;
  line-height: 1.6;
}

@media (max-width: 600px) {
  .adv-fields-grid { grid-template-columns: 1fr; }
}