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

/* ── Shared structural variables ────────────────────────────────────────── */
:root {
  --radius: 12px;
  --radius-sm: 8px;
  --font: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  --mono: 'JetBrains Mono', 'Fira Code', monospace;
}

/* ── Theme: Dark (default) ──────────────────────────────────────────────── */
[data-theme="dark"] {
  --bg: #0f1117;
  --bg-card: #1a1d27;
  --bg-card-hover: #222639;
  --border: #2a2e3d;
  --text: #e4e4e7;
  --text-muted: #8b8fa3;
  --primary: #6366f1;
  --primary-hover: #818cf8;
  --primary-bg: rgba(99, 102, 241, 0.1);
  --success: #22c55e;
  --success-bg: rgba(34, 197, 94, 0.1);
  --warning: #f59e0b;
  --warning-bg: rgba(245, 158, 11, 0.1);
  --danger: #ef4444;
  --danger-bg: rgba(239, 68, 68, 0.1);
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.3);
  --h1-gradient-from: #6366f1;
  --h1-gradient-to: #a78bfa;
  --code-bg: #0d1117;
  --code-text: #c9d1d9;
  --modal-overlay: rgba(0, 0, 0, 0.7);
  --btn-disabled-bg: #555;
  --btn-disabled-text: #aaa;
  --hint-text: #888;
  --required-color: #e74c3c;
}

/* ── Theme: Light ──────────────────────────────────────────────────────── */
[data-theme="light"] {
  --bg: #f5f5f7;
  --bg-card: #ffffff;
  --bg-card-hover: #f0f0f5;
  --border: #d1d5db;
  --text: #1f2937;
  --text-muted: #6b7280;
  --primary: #4f46e5;
  --primary-hover: #6366f1;
  --primary-bg: rgba(79, 70, 229, 0.08);
  --success: #16a34a;
  --success-bg: rgba(22, 163, 74, 0.08);
  --warning: #d97706;
  --warning-bg: rgba(217, 119, 6, 0.08);
  --danger: #dc2626;
  --danger-bg: rgba(220, 38, 38, 0.08);
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.08);
  --h1-gradient-from: #4f46e5;
  --h1-gradient-to: #7c3aed;
  --code-bg: #f8f9fa;
  --code-text: #24292f;
  --modal-overlay: rgba(0, 0, 0, 0.4);
  --btn-disabled-bg: #d1d5db;
  --btn-disabled-text: #9ca3af;
  --hint-text: #6b7280;
  --required-color: #dc2626;
}

/* ── Theme: Fancy ──────────────────────────────────────────────────────── */
[data-theme="fancy"] {
  --bg: #faf5ff;
  --bg-card: #ffffff;
  --bg-card-hover: #f3e8ff;
  --border: #e0c4ff;
  --text: #2e1065;
  --text-muted: #7e22ce;
  --primary: #a855f7;
  --primary-hover: #c084fc;
  --primary-bg: rgba(168, 85, 247, 0.1);
  --success: #16a34a;
  --success-bg: rgba(22, 163, 74, 0.1);
  --warning: #ea580c;
  --warning-bg: rgba(234, 88, 12, 0.1);
  --danger: #e11d48;
  --danger-bg: rgba(225, 29, 72, 0.1);
  --shadow: 0 4px 24px rgba(168, 85, 247, 0.12);
  --h1-gradient-from: #a855f7;
  --h1-gradient-to: #ec4899;
  --code-bg: #fdf4ff;
  --code-text: #3b0764;
  --modal-overlay: rgba(46, 16, 101, 0.4);
  --btn-disabled-bg: #e0c4ff;
  --btn-disabled-text: #a78bfa;
  --hint-text: #9333ea;
  --required-color: #e11d48;
}

/* ── Theme: Hacker ─────────────────────────────────────────────────────── */
[data-theme="hacker"] {
  --bg: #0a0e1a;
  --bg-card: #0f1628;
  --bg-card-hover: #141d36;
  --border: #1a2744;
  --text: #e0e8ff;
  --text-muted: #7b8db8;
  --primary: #facc15;
  --primary-hover: #fde047;
  --primary-bg: rgba(250, 204, 21, 0.1);
  --success: #22c55e;
  --success-bg: rgba(34, 197, 94, 0.12);
  --warning: #fb923c;
  --warning-bg: rgba(251, 146, 60, 0.1);
  --danger: #f87171;
  --danger-bg: rgba(248, 113, 113, 0.1);
  --shadow: 0 4px 24px rgba(0, 0, 0, 0.5);
  --h1-gradient-from: #facc15;
  --h1-gradient-to: #22c55e;
  --code-bg: #060a14;
  --code-text: #e0e8ff;
  --modal-overlay: rgba(0, 0, 0, 0.8);
  --btn-disabled-bg: #1a2744;
  --btn-disabled-text: #4b6590;
  --hint-text: #7b8db8;
  --required-color: #f87171;
}
[data-theme="hacker"] .btn-primary { color: #0a0e1a; }
[data-theme="hacker"] .btn-primary:hover { color: #0a0e1a; }

/* ── Theme: Matrix ─────────────────────────────────────────────────────── */
[data-theme="matrix"] {
  --bg: #0a0a0a;
  --bg-card: #0f120f;
  --bg-card-hover: #141a14;
  --border: #1a2e1a;
  --text: #33ff33;
  --text-muted: #1a991a;
  --primary: #00ff41;
  --primary-hover: #33ff66;
  --primary-bg: rgba(0, 255, 65, 0.08);
  --success: #00ff41;
  --success-bg: rgba(0, 255, 65, 0.1);
  --warning: #ccff00;
  --warning-bg: rgba(204, 255, 0, 0.08);
  --danger: #ff3333;
  --danger-bg: rgba(255, 51, 51, 0.1);
  --shadow: 0 4px 24px rgba(0, 255, 65, 0.06);
  --h1-gradient-from: #00ff41;
  --h1-gradient-to: #00cc33;
  --code-bg: #050805;
  --code-text: #33ff33;
  --modal-overlay: rgba(0, 0, 0, 0.85);
  --btn-disabled-bg: #1a2e1a;
  --btn-disabled-text: #1a6e1a;
  --hint-text: #1a991a;
  --required-color: #ff3333;
}
[data-theme="matrix"] .btn-primary { color: #0a0a0a; }
[data-theme="matrix"] .btn-primary:hover { color: #0a0a0a; }
[data-theme="matrix"] .btn-success { color: #0a0a0a; }

/* ── Theme: Pink ───────────────────────────────────────────────────────── */
[data-theme="pink"] {
  --bg: #fff0f6;
  --bg-card: #ffffff;
  --bg-card-hover: #ffe0ef;
  --border: #f9a8d4;
  --text: #4a0e2e;
  --text-muted: #9d174d;
  --primary: #ec4899;
  --primary-hover: #f472b6;
  --primary-bg: rgba(236, 72, 153, 0.1);
  --success: #16a34a;
  --success-bg: rgba(22, 163, 74, 0.1);
  --warning: #d97706;
  --warning-bg: rgba(217, 119, 6, 0.1);
  --danger: #e11d48;
  --danger-bg: rgba(225, 29, 72, 0.1);
  --shadow: 0 4px 24px rgba(236, 72, 153, 0.1);
  --h1-gradient-from: #ec4899;
  --h1-gradient-to: #a855f7;
  --code-bg: #fdf2f8;
  --code-text: #4a0e2e;
  --modal-overlay: rgba(74, 14, 46, 0.4);
  --btn-disabled-bg: #f9a8d4;
  --btn-disabled-text: #db2777;
  --hint-text: #be185d;
  --required-color: #e11d48;
}

body {
  font-family: var(--font);
  background: var(--bg);
  color: var(--text);
  line-height: 1.6;
  min-height: 100vh;
}

a { color: var(--primary); text-decoration: none; }
a:hover { color: var(--primary-hover); }

/* ── Layout ─────────────────────────────────────────────────────────────── */
.container {
  max-width: 1400px;
  margin: 0 auto;
  padding: 2rem 1.5rem;
}

.header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 1rem 2rem;
  background: var(--bg-card);
  border-bottom: 1px solid var(--border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.header h1 {
  font-size: 1.25rem;
  font-weight: 700;
  background: linear-gradient(135deg, var(--h1-gradient-from), var(--h1-gradient-to));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.header-actions {
  display: flex;
  gap: 0.75rem;
  align-items: center;
}

/* ── Cards ──────────────────────────────────────────────────────────────── */
.card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  margin-bottom: 1.5rem;
  box-shadow: var(--shadow);
}

.card h2 {
  font-size: 1.1rem;
  margin-bottom: 1rem;
  color: var(--text);
}

.card h3 {
  font-size: 0.95rem;
  margin-bottom: 0.75rem;
  color: var(--text-muted);
}

/* ── Forms ──────────────────────────────────────────────────────────────── */
.form-group {
  margin-bottom: 1rem;
}

.form-group label {
  display: block;
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text-muted);
  margin-bottom: 0.35rem;
}

input[type="text"],
input[type="email"],
input[type="password"],
input[type="date"],
input[type="file"],
select,
textarea {
  width: 100%;
  padding: 0.65rem 0.85rem;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text);
  font-size: 0.9rem;
  font-family: var(--font);
  transition: border-color 0.2s;
}

input:focus, select:focus, textarea:focus {
  outline: none;
  border-color: var(--primary);
  box-shadow: 0 0 0 3px var(--primary-bg);
}

textarea {
  min-height: 120px;
  resize: vertical;
  font-family: var(--mono);
  font-size: 0.85rem;
}

/* ── Buttons ────────────────────────────────────────────────────────────── */
.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.6rem 1.2rem;
  border: none;
  border-radius: var(--radius-sm);
  font-size: 0.85rem;
  font-weight: 600;
  font-family: var(--font);
  cursor: pointer;
  transition: all 0.2s;
}

.btn-primary {
  background: var(--primary);
  color: #fff;
}
.btn-primary:hover { background: var(--primary-hover); }

.btn-success {
  background: var(--success);
  color: #fff;
}
.btn-success:hover { background: #16a34a; }

.btn-danger {
  background: var(--danger);
  color: #fff;
}
.btn-danger:hover { background: #dc2626; }

.btn-outline {
  background: transparent;
  border: 1px solid var(--border);
  color: var(--text);
}
.btn-outline:hover {
  background: var(--bg-card-hover);
  border-color: var(--primary);
}

.btn-sm {
  padding: 0.35rem 0.75rem;
  font-size: 0.78rem;
}

.btn:disabled {
  opacity: 0.5;
  cursor: not-allowed;
}

/* ── Login Box ──────────────────────────────────────────────────────────── */
.login-container {
  display: flex;
  justify-content: center;
  align-items: center;
  min-height: 100vh;
  padding: 2rem;
}

.login-box {
  width: 100%;
  max-width: 420px;
}

.login-box h1 {
  text-align: center;
  margin-bottom: 0.5rem;
  font-size: 1.5rem;
  background: linear-gradient(135deg, var(--h1-gradient-from), var(--h1-gradient-to));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.login-box .subtitle {
  text-align: center;
  color: var(--text-muted);
  font-size: 0.9rem;
  margin-bottom: 1.5rem;
}

/* ── Tabs ───────────────────────────────────────────────────────────────── */
.tabs {
  display: flex;
  gap: 0;
  border-bottom: 1px solid var(--border);
  margin-bottom: 1.5rem;
}

.tab {
  padding: 0.75rem 1.25rem;
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text-muted);
  cursor: pointer;
  border-bottom: 2px solid transparent;
  transition: all 0.2s;
  background: none;
  border-top: none;
  border-left: none;
  border-right: none;
  font-family: var(--font);
}

.tab:hover { color: var(--text); }
.tab.active {
  color: var(--primary);
  border-bottom-color: var(--primary);
}

.tab-content { display: none; }
.tab-content.active { display: block; }

/* ── Tables ─────────────────────────────────────────────────────────────── */
.table-wrap {
  overflow-x: auto;
}

table {
  width: max-content;
  min-width: 100%;
  border-collapse: collapse;
  font-size: 0.85rem;
}

th, td {
  padding: 0.65rem 0.85rem;
  text-align: left;
  border-bottom: 1px solid var(--border);
  white-space: nowrap;
}

th {
  color: var(--text-muted);
  font-weight: 600;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}

tr:hover td { background: var(--bg-card-hover); }

/* ── Badges ─────────────────────────────────────────────────────────────── */
.badge {
  display: inline-block;
  padding: 0.2rem 0.6rem;
  border-radius: 999px;
  font-size: 0.72rem;
  font-weight: 600;
}

.badge-success { background: var(--success-bg); color: var(--success); }
.badge-warning { background: var(--warning-bg); color: var(--warning); }
.badge-danger { background: var(--danger-bg); color: var(--danger); }
.badge-primary { background: var(--primary-bg); color: var(--primary); }

/* ── Problem Card ───────────────────────────────────────────────────────── */
.problem-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  margin-bottom: 1.25rem;
  transition: border-color 0.2s;
}

.problem-card:hover { border-color: var(--primary); }

.problem-card .problem-header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 1rem;
}

.problem-card .problem-number {
  font-weight: 700;
  color: var(--primary);
  font-size: 0.9rem;
}

.problem-card .statement {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 1rem;
  margin-bottom: 0.75rem;
  font-family: var(--mono);
  font-size: 0.85rem;
  white-space: pre-wrap;
  line-height: 1.5;
}

.problem-card .input-data {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 0.75rem;
  font-family: var(--mono);
  font-size: 0.83rem;
  white-space: pre-wrap;
  color: var(--warning);
}

.problem-card .input-data-label {
  font-size: 0.78rem;
  color: var(--text-muted);
  margin-bottom: 0.3rem;
  font-weight: 600;
}

/* ── File Upload ────────────────────────────────────────────────────────── */
.file-upload-area {
  border: 2px dashed var(--border);
  border-radius: var(--radius);
  padding: 1.5rem;
  text-align: center;
  cursor: pointer;
  transition: all 0.2s;
  margin: 0.75rem 0;
}

.file-upload-area:hover {
  border-color: var(--primary);
  background: var(--primary-bg);
}

.file-upload-area .icon { font-size: 1.5rem; margin-bottom: 0.5rem; }
.file-upload-area p { color: var(--text-muted); font-size: 0.85rem; }
.file-list { margin-top: 0.5rem; }
.file-item {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 0.4rem 0.75rem;
  background: var(--bg);
  border-radius: var(--radius-sm);
  margin-bottom: 0.3rem;
  font-size: 0.83rem;
}

/* ── Ranking Board ──────────────────────────────────────────────────────── */
.ranking-item {
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 0.85rem 1rem;
  border-bottom: 1px solid var(--border);
  transition: background 0.2s;
}

.ranking-item:hover { background: var(--bg-card-hover); }

.ranking-position {
  font-size: 1.2rem;
  font-weight: 800;
  min-width: 2rem;
  text-align: center;
}

.ranking-position.gold { color: #fbbf24; }
.ranking-position.silver { color: #94a3b8; }
.ranking-position.bronze { color: #d97706; }

.ranking-avatar {
  width: 42px;
  height: 42px;
  border-radius: 50%;
  object-fit: cover;
  border: 2px solid var(--border);
  background: var(--bg);
}

.ranking-avatar-placeholder {
  width: 42px;
  height: 42px;
  border-radius: 50%;
  background: var(--primary-bg);
  display: flex;
  align-items: center;
  justify-content: center;
  font-weight: 700;
  color: var(--primary);
  font-size: 1rem;
  border: 2px solid var(--border);
}

.ranking-info { flex: 1; }
.ranking-nickname { font-weight: 600; font-size: 0.95rem; }
.ranking-score {
  font-weight: 700;
  font-size: 1.1rem;
  color: var(--primary);
}

/* ── Timer ──────────────────────────────────────────────────────────────── */
.timer {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.4rem 0.85rem;
  background: var(--danger-bg);
  border-radius: 999px;
  font-size: 0.85rem;
  font-weight: 600;
  color: var(--danger);
  font-family: var(--mono);
}

.timer.safe { background: var(--success-bg); color: var(--success); }

/* ── Alert ──────────────────────────────────────────────────────────────── */
.alert {
  padding: 0.85rem 1.1rem;
  border-radius: var(--radius-sm);
  margin-bottom: 1rem;
  font-size: 0.85rem;
}

.alert-error { background: var(--danger-bg); color: var(--danger); border: 1px solid rgba(239,68,68,0.2); }
.alert-success { background: var(--success-bg); color: var(--success); border: 1px solid rgba(34,197,94,0.2); }
.alert-info { background: var(--primary-bg); color: var(--primary); border: 1px solid rgba(99,102,241,0.2); }

/* ── Grid layout ────────────────────────────────────────────────────────── */
.grid-2 {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1.25rem;
}

.grid-3 {
  display: grid;
  grid-template-columns: 1fr 1fr 1fr;
  gap: 1rem;
}

/* ── Stat card ──────────────────────────────────────────────────────────── */
.stat-card {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem;
  text-align: center;
}

.stat-value {
  font-size: 1.8rem;
  font-weight: 800;
  color: var(--primary);
}

.stat-label {
  font-size: 0.78rem;
  color: var(--text-muted);
  margin-top: 0.25rem;
}

/* ── Submission viewer (admin) ──────────────────────────────────────────── */
.code-viewer {
  background: var(--code-bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  padding: 1rem;
  font-family: var(--mono);
  font-size: 0.82rem;
  overflow-x: auto;
  white-space: pre;
  color: var(--code-text);
  max-height: 400px;
  overflow-y: auto;
}

/* ── Modal ──────────────────────────────────────────────────────────────── */
.modal-overlay {
  position: fixed;
  top: 0; left: 0; right: 0; bottom: 0;
  background: var(--modal-overlay);
  display: flex;
  justify-content: center;
  align-items: center;
  z-index: 1000;
  padding: 2rem;
}

.modal {
  background: var(--bg-card);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 2rem;
  width: 100%;
  max-width: 600px;
  max-height: 80vh;
  overflow-y: auto;
  box-shadow: var(--shadow);
}

.modal h2 { margin-bottom: 1rem; }

.modal-actions {
  display: flex;
  gap: 0.75rem;
  justify-content: flex-end;
  margin-top: 1.5rem;
}

/* ── Responsive ─────────────────────────────────────────────────────────── */
@media (max-width: 768px) {
  .grid-2, .grid-3 { grid-template-columns: 1fr; }
  .header { flex-direction: column; gap: 0.75rem; }
  .container { padding: 1rem; }
}

/* ── Utilities ──────────────────────────────────────────────────────────── */
.hidden { display: none !important; }
.mt-1 { margin-top: 0.5rem; }
.mt-2 { margin-top: 1rem; }
.mt-3 { margin-top: 1.5rem; }
.mb-1 { margin-bottom: 0.5rem; }
.mb-2 { margin-bottom: 1rem; }
.text-center { text-align: center; }
.text-muted { color: var(--text-muted); }
.text-sm { font-size: 0.83rem; }
.flex { display: flex; }
.flex-between { display: flex; justify-content: space-between; align-items: center; }
.gap-1 { gap: 0.5rem; }
.gap-2 { gap: 1rem; }

/* ── Theme Switcher ────────────────────────────────────────────────────── */
.theme-switcher {
  position: relative;
  display: inline-flex;
  align-items: center;
}

.theme-switcher select {
  width: auto;
  padding: 0.3rem 1.8rem 0.3rem 0.6rem;
  font-size: 0.75rem;
  font-weight: 600;
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius-sm);
  color: var(--text);
  cursor: pointer;
  appearance: none;
  -webkit-appearance: none;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='10' height='6'%3E%3Cpath d='M0 0l5 6 5-6z' fill='%238b8fa3'/%3E%3C/svg%3E");
  background-repeat: no-repeat;
  background-position: right 0.5rem center;
}

.theme-switcher select:focus {
  outline: none;
  border-color: var(--primary);
}