:root {
  --bg-dark: #0f1219;
  --bg-panel: #161b22;
  --bg-card: #0d1117;
  --bg-input: #0d1117;
  --border: #30363d;
  --text-main: #c9d1d9;
  --text-muted: #8b949e;
  --text-bright: #ffffff;
  --accent-green: #238636;
  --accent-blue: #1f6feb;
  --accent-red: #da3633;
  --brand: #88cc14;
  --radius: 8px;
  --radius-sm: 6px;
}

* { margin: 0; padding: 0; box-sizing: border-box; font-family: 'Segoe UI', -apple-system, sans-serif; }

body { background-color: var(--bg-dark); color: var(--text-main); display: flex; min-height: 100vh; }

::selection { background: rgba(136, 204, 20, 0.25); color: var(--text-bright); }

/* SCROLLBAR */
::-webkit-scrollbar { width: 6px; }
::-webkit-scrollbar-track { background: var(--bg-dark); }
::-webkit-scrollbar-thumb { background: var(--border); border-radius: 3px; }

/* SIDEBAR */
.sidebar {
  width: 260px; background-color: var(--bg-panel); border-right: 1px solid var(--border);
  display: flex; flex-direction: column; position: fixed; height: 100%; z-index: 100;
}

.logo {
  padding: 0 25px 25px; font-size: 24px; font-weight: 800; color: var(--brand);
  border-bottom: 1px solid var(--border); padding-top: 25px; letter-spacing: 1px;
}
.logo i { margin-right: 10px; }

.nav-links { list-style: none; margin-top: 20px; }
.nav-links a {
  display: flex; align-items: center; padding: 12px 25px; color: var(--text-main);
  text-decoration: none; border-left: 4px solid transparent; transition: all 0.2s;
}
.nav-links a:hover { background-color: rgba(255,255,255,0.05); }
.nav-links a.active, .nav-links a.active:hover {
  background-color: rgba(136, 204, 20, 0.1); border-left: 4px solid var(--brand); color: var(--text-bright);
}
.nav-links i { margin-right: 15px; width: 20px; text-align: center; }

.sidebar-footer {
  margin-top: auto; padding: 20px 25px; border-top: 1px solid var(--border);
  text-align: center;
}
.sidebar-points {
  font-size: 14px; color: var(--brand); font-weight: 700; margin-bottom: 4px;
}
.sidebar-points i { margin-right: 6px; }
.sidebar-version { font-size: 11px; color: var(--text-muted); }

.sidebar-credit {
  margin-top: 12px; padding-top: 12px; border-top: 1px solid var(--border);
  display: flex; flex-direction: column; align-items: center; gap: 6px;
}
.sidebar-credit a {
  font-size: 11px; color: var(--text-muted); text-decoration: none;
  display: inline-flex; align-items: center; gap: 6px; transition: color 0.2s;
}
.sidebar-credit a:hover { color: var(--brand); }
.sidebar-credit a i { font-size: 11px; }

/* MAIN CONTENT */
.main-content { margin-left: 260px; padding: 40px; flex: 1; min-height: 100vh; }

.top-bar {
  display: flex; justify-content: space-between; align-items: center;
  margin-bottom: 30px; padding-bottom: 15px; border-bottom: 1px solid var(--border);
}
.top-bar h1 { font-size: 28px; color: var(--text-bright); }
.top-bar-stats { display: flex; gap: 16px; }

.stat-pill {
  padding: 6px 14px; border-radius: 20px; background: var(--bg-panel);
  border: 1px solid var(--border); font-size: 13px; color: var(--text-muted);
}
.stat-pill strong { color: var(--brand); }

/* PROGRESS */
.progress-section { max-width: 600px; margin-bottom: 30px; }
.progress-bar-container { display: flex; align-items: center; gap: 16px; }
.progress-bar {
  flex: 1; height: 8px; background: var(--bg-panel);
  border-radius: 4px; overflow: hidden; border: 1px solid var(--border);
}
.progress-fill {
  height: 100%; background: linear-gradient(90deg, var(--brand), var(--accent-blue));
  border-radius: 4px; transition: width 0.6s ease; width: 0%;
}
.progress-text { font-family: monospace; font-size: 0.85rem; color: var(--brand); min-width: 60px; text-align: right; }

/* TIER SECTION */
.tier-section { margin-bottom: 40px; }

.tier-header {
  display: flex; align-items: center; gap: 12px; margin-bottom: 20px;
  padding-bottom: 10px; border-bottom: 1px solid var(--border);
}
.tier-icon { font-size: 1.2rem; }
.tier-title { font-size: 16px; font-weight: 700; letter-spacing: 1px; text-transform: uppercase; }
.tier-badge {
  font-family: monospace; font-size: 11px; padding: 3px 10px; border-radius: var(--radius-sm);
  background: rgba(255,255,255,0.05); border: 1px solid var(--border); color: var(--text-muted);
}

.tier-beginner .tier-title { color: #3fb950; }
.tier-intermediate .tier-title { color: #d29922; }
.tier-advanced .tier-title { color: #f85149; }
.tier-expert .tier-title { color: #bc8cff; }
.tier-boss .tier-title { color: #ff7b72; }

/* CHALLENGE GRID */
.challenge-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(320px, 1fr)); gap: 20px; }

.challenge-card {
  position: relative; background: var(--bg-panel); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 24px; cursor: pointer; transition: all 0.3s; overflow: hidden;
  display: flex; flex-direction: column;
  text-decoration: none; color: var(--text-main);
}
.challenge-card, .challenge-card:hover, .challenge-card:visited { text-decoration: none; }
.challenge-card:hover { transform: translateY(-4px); border-color: var(--brand); }

.challenge-card.solved { opacity: 0.7; border-color: var(--accent-green); }

.challenge-card.solved::after {
  content: 'COMPLETED'; position: absolute; top: 12px; right: 12px;
  font-family: monospace; font-size: 10px; font-weight: 700; letter-spacing: 1px;
  color: #3fb950; background: rgba(35,134,54,0.15); padding: 4px 10px;
  border-radius: var(--radius-sm); border: 1px solid rgba(35,134,54,0.3);
}

.challenge-card.locked { opacity: 0.4; pointer-events: none; filter: grayscale(0.5); }
.challenge-card.locked::after {
  content: 'LOCKED'; position: absolute; top: 12px; right: 12px;
  font-family: monospace; font-size: 10px; font-weight: 700; letter-spacing: 1px;
  color: var(--text-muted); background: rgba(255,255,255,0.05);
  padding: 4px 10px; border-radius: var(--radius-sm);
}

.card-number {
  font-family: monospace; font-size: 11px; font-weight: 600;
  color: var(--text-muted); margin-bottom: 8px; letter-spacing: 1px;
}

.card-title { font-size: 18px; font-weight: 700; color: var(--text-bright); margin-bottom: 8px; }

.card-category {
  display: inline-block; font-family: monospace; font-size: 10px;
  padding: 3px 8px; border-radius: var(--radius-sm); margin-bottom: 12px;
  letter-spacing: 0.5px; text-transform: uppercase;
}

.cat-info-disclosure { background: rgba(31, 111, 235, 0.15); color: #58a6ff; border: 1px solid rgba(31, 111, 235, 0.3); }
.cat-sensitive-data { background: rgba(210, 153, 34, 0.15); color: #d29922; border: 1px solid rgba(210, 153, 34, 0.3); }
.cat-open-redirect { background: rgba(255, 123, 114, 0.15); color: #ff7b72; border: 1px solid rgba(255, 123, 114, 0.3); }
.cat-xss { background: rgba(248, 81, 73, 0.15); color: #f85149; border: 1px solid rgba(248, 81, 73, 0.3); }
.cat-broken-auth { background: rgba(188, 140, 255, 0.15); color: #bc8cff; border: 1px solid rgba(188, 140, 255, 0.3); }
.cat-idor { background: rgba(136, 204, 20, 0.15); color: var(--brand); border: 1px solid rgba(136, 204, 20, 0.3); }
.cat-crypto { background: rgba(63, 185, 80, 0.15); color: #3fb950; border: 1px solid rgba(63, 185, 80, 0.3); }
.cat-sqli { background: rgba(248, 81, 73, 0.15); color: #f85149; border: 1px solid rgba(248, 81, 73, 0.3); }
.cat-jwt { background: rgba(255, 123, 114, 0.15); color: #ff7b72; border: 1px solid rgba(255, 123, 114, 0.3); }
.cat-template-injection { background: rgba(188, 140, 255, 0.15); color: #bc8cff; border: 1px solid rgba(188, 140, 255, 0.3); }
.cat-path-traversal { background: rgba(58, 166, 255, 0.15); color: #58a6ff; border: 1px solid rgba(58, 166, 255, 0.3); }
.cat-prototype-pollution { background: rgba(188, 140, 255, 0.15); color: #bc8cff; border: 1px solid rgba(188, 140, 255, 0.3); }
.cat-dom-clobbering { background: rgba(210, 153, 34, 0.15); color: #d29922; border: 1px solid rgba(210, 153, 34, 0.3); }
.cat-race-condition { background: rgba(63, 185, 80, 0.15); color: #3fb950; border: 1px solid rgba(63, 185, 80, 0.3); }
.cat-multi-stage { background: rgba(255, 123, 114, 0.15); color: #ff7b72; border: 1px solid rgba(255, 123, 114, 0.3); }

.card-description { font-size: 14px; color: var(--text-muted); line-height: 1.5; margin-bottom: 16px; flex: 1; }

.card-footer { display: flex; align-items: center; justify-content: space-between; margin-top: auto; }
.card-points { font-family: monospace; font-size: 14px; color: #d29922; font-weight: 600; }

.card-difficulty {
  font-family: monospace; font-size: 10px; letter-spacing: 1px; text-transform: uppercase;
  padding: 3px 10px; border-radius: var(--radius-sm);
}
.diff-beginner { color: #3fb950; background: rgba(63, 185, 80, 0.1); }
.diff-intermediate { color: #d29922; background: rgba(210, 153, 34, 0.1); }
.diff-advanced { color: #f85149; background: rgba(248, 81, 73, 0.1); }
.diff-expert { color: #bc8cff; background: rgba(188, 140, 255, 0.1); }
.diff-boss { color: #ff7b72; background: rgba(255, 123, 114, 0.1); }

/* MODAL */
.modal-overlay {
  position: fixed; inset: 0; z-index: 1000;
  background: rgba(0,0,0,0.8); display: flex; align-items: center; justify-content: center;
  opacity: 0; visibility: hidden; transition: all 0.3s;
}
.modal-overlay.active { opacity: 1; visibility: visible; }

.modal {
  background: var(--bg-panel); border: 1px solid var(--border); border-radius: var(--radius);
  padding: 40px; max-width: 500px; width: 90%;
  transform: scale(0.9); transition: transform 0.3s;
  box-shadow: 0 24px 80px rgba(0,0,0,0.5);
}
.modal-overlay.active .modal { transform: scale(1); }

.modal-title { font-size: 22px; font-weight: 700; color: var(--text-bright); margin-bottom: 24px; text-align: center; }
.modal-title i { margin-right: 10px; color: var(--brand); }

.modal-close {
  position: absolute; top: 16px; right: 16px; background: none; border: none;
  color: var(--text-muted); font-size: 24px; cursor: pointer; transition: color 0.3s;
}
.modal-close:hover { color: var(--accent-red); }

/* FORMS */
.form-group { margin-bottom: 20px; }
.form-group label { display: block; margin-bottom: 8px; font-weight: 600; font-size: 13px; }

.form-control {
  width: 100%; padding: 12px; background: var(--bg-input);
  border: 1px solid var(--border); border-radius: var(--radius-sm);
  color: var(--text-main); font-size: 14px; outline: none; transition: border-color 0.3s;
}
.form-control:focus { border-color: var(--brand); box-shadow: 0 0 0 3px rgba(136, 204, 20, 0.15); }
.form-control::placeholder { color: var(--text-muted); }

/* BUTTONS */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 10px 20px; font-size: 14px; font-weight: 600;
  border: none; border-radius: var(--radius-sm); cursor: pointer;
  transition: all 0.2s; color: white;
}

.btn-primary { background: var(--accent-green); }
.btn-primary:hover { background: #2ea043; }

.btn-ghost {
  background: transparent; border: 1px solid var(--border); color: var(--text-muted);
}
.btn-ghost:hover { border-color: var(--brand); color: var(--brand); }

.btn-block { width: 100%; }

/* UTILITY */
.text-green { color: #3fb950; }
.text-red { color: #f85149; }
.mt-1 { margin-top: 8px; }
.mt-2 { margin-top: 16px; }
.hidden { display: none !important; }

@media (max-width: 768px) {
  .sidebar { width: 200px; }
  .main-content { margin-left: 200px; padding: 20px; }
  .challenge-grid { grid-template-columns: 1fr; }
  .top-bar { flex-direction: column; align-items: flex-start; gap: 12px; }
}

/* TOAST NOTIFICATIONS */
.toast-container {
  position: fixed; top: 20px; right: 20px; z-index: 2000;
  display: flex; flex-direction: column; gap: 10px;
}
.toast {
  background: var(--bg-panel); border: 1px solid var(--border); color: var(--text-main);
  padding: 12px 16px; border-radius: var(--radius); font-size: 13px;
  display: flex; align-items: center; gap: 10px; min-width: 220px;
  box-shadow: 0 8px 24px rgba(0,0,0,0.4);
}
.toast-success { border-color: var(--accent-green); color: #3fb950; }
.toast-error { border-color: var(--accent-red); color: #f85149; }
.toast-info { border-color: var(--accent-blue); color: #58a6ff; }

@media (max-width: 768px) {
  .toast-container { top: auto; bottom: 12px; right: 12px; left: 12px; }
  .toast { width: 100%; }
}

/* CATEGORY TABS */
.category-tabs {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-bottom: 30px;
  padding-bottom: 20px;
  border-bottom: 1px solid var(--border);
}
.cat-tab {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 16px;
  border-radius: var(--radius-sm);
  background: var(--bg-panel);
  border: 1px solid var(--border);
  color: var(--text-main);
  font-size: 13px;
  font-weight: 600;
  cursor: pointer;
  transition: all 0.2s;
}
.cat-tab i { color: var(--cat-color, var(--text-muted)); }
.cat-tab:hover {
  border-color: var(--cat-color, var(--brand));
  color: var(--cat-color, var(--brand));
}
.cat-tab.active {
  background: var(--cat-color, var(--brand));
  border-color: var(--cat-color, var(--brand));
  color: #0f1219;
}
.cat-tab.active i { color: #0f1219; }
.cat-count {
  font-family: monospace;
  font-size: 11px;
  opacity: 0.8;
  margin-left: 4px;
}

/* CATEGORY SECTIONS */
.category-section { margin-bottom: 40px; }
.category-header {
  display: flex;
  align-items: center;
  gap: 12px;
  margin-bottom: 20px;
  padding-bottom: 10px;
  border-bottom: 1px solid var(--border);
}
.category-icon {
  width: 36px; height: 36px;
  display: flex; align-items: center; justify-content: center;
  background: rgba(255,255,255,0.05);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-size: 16px;
}
.category-title {
  font-size: 18px;
  font-weight: 700;
  letter-spacing: 1px;
  text-transform: uppercase;
}

/* Category badges */
.cat-web { background: rgba(136, 204, 20, 0.15); color: var(--brand); border: 1px solid rgba(136, 204, 20, 0.3); }
.cat-binary { background: rgba(255, 123, 114, 0.15); color: #ff7b72; border: 1px solid rgba(255, 123, 114, 0.3); }
.cat-network { background: rgba(88, 166, 255, 0.15); color: #58a6ff; border: 1px solid rgba(88, 166, 255, 0.3); }
.cat-forensics { background: rgba(210, 153, 34, 0.15); color: #d29922; border: 1px solid rgba(210, 153, 34, 0.3); }
.cat-reverse { background: rgba(188, 140, 255, 0.15); color: #bc8cff; border: 1px solid rgba(188, 140, 255, 0.3); }
.cat-stego { background: rgba(63, 185, 80, 0.15); color: #3fb950; border: 1px solid rgba(63, 185, 80, 0.3); }
.cat-recon { background: rgba(248, 81, 73, 0.15); color: #f85149; border: 1px solid rgba(248, 81, 73, 0.3); }
.cat-academic { background: rgba(121, 192, 255, 0.15); color: #79c0ff; border: 1px solid rgba(121, 192, 255, 0.3); }

@media (max-width: 768px) {
  .category-tabs { gap: 8px; }
  .cat-tab { padding: 6px 10px; font-size: 12px; }
}

/* FILTER BAR */
.filter-bar {
  display: flex; align-items: center; gap: 12px; flex-wrap: wrap;
  margin-bottom: 24px;
}
.search-wrap {
  position: relative; flex: 1; min-width: 220px;
}
.search-wrap i {
  position: absolute; left: 12px; top: 50%; transform: translateY(-50%);
  color: var(--text-muted); font-size: 13px; pointer-events: none;
}
.filter-search {
  width: 100%; padding: 10px 12px 10px 34px;
  background: var(--bg-input); border: 1px solid var(--border);
  border-radius: var(--radius-sm); color: var(--text-main); font-size: 14px;
  outline: none; transition: border-color 0.2s;
}
.filter-search:focus { border-color: var(--brand); box-shadow: 0 0 0 3px rgba(136,204,20,0.15); }
.filter-search::placeholder { color: var(--text-muted); }
.filter-select {
  padding: 10px 12px; background: var(--bg-input); border: 1px solid var(--border);
  border-radius: var(--radius-sm); color: var(--text-main); font-size: 13px;
  outline: none; cursor: pointer;
}
.filter-select:focus { border-color: var(--brand); }
.filter-toggle {
  display: inline-flex; align-items: center; gap: 8px; font-size: 13px;
  color: var(--text-muted); cursor: pointer; -webkit-user-select: none; user-select: none; white-space: nowrap;
}
.filter-toggle input { accent-color: var(--brand); width: 15px; height: 15px; cursor: pointer; }

/* EMPTY STATE */
.empty-state {
  text-align: center; padding: 60px 20px; color: var(--text-muted);
}
.empty-state i { font-size: 42px; margin-bottom: 14px; opacity: 0.5; display: block; }
.empty-state p { font-size: 15px; }

/* HIGHLIGHT (search match) */
.challenge-card mark {
  background: rgba(136,204,20,0.25); color: var(--text-bright);
  border-radius: 3px; padding: 0 2px;
}

/* ACHIEVEMENTS STRIP */
.achievements-strip {
  display: flex; gap: 10px; flex-wrap: wrap; margin-bottom: 26px;
}
.achievements-strip:empty { display: none; }
.badge-chip {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 7px 14px; border-radius: 999px; font-size: 12.5px; font-weight: 600;
  background: rgba(136,204,20,0.12); border: 1px solid rgba(136,204,20,0.35);
  color: var(--brand);
}
.badge-chip .badge-emoji { font-size: 14px; }

/* ACHIEVEMENTS MODAL GRID */
.modal-wide { max-width: 640px; }
.badge-grid {
  display: grid; grid-template-columns: repeat(auto-fill, minmax(180px, 1fr));
  gap: 14px; max-height: 60vh; overflow-y: auto;
}
.badge {
  border: 1px solid var(--border); border-radius: var(--radius);
  padding: 16px; background: var(--bg-card); transition: all 0.2s;
}
.badge.earned { border-color: rgba(136,204,20,0.45); background: rgba(136,204,20,0.06); }
.badge.locked { opacity: 0.5; filter: grayscale(0.4); }
.badge-top { display: flex; align-items: center; gap: 10px; margin-bottom: 8px; }
.badge-icon { font-size: 22px; }
.badge-name { font-weight: 700; font-size: 14px; color: var(--text-bright); }
.badge-desc { font-size: 12px; color: var(--text-muted); line-height: 1.4; }
.badge-status {
  margin-top: 10px; font-family: monospace; font-size: 10px; letter-spacing: 1px;
  text-transform: uppercase;
}
.badge.earned .badge-status { color: #3fb950; }
.badge.locked .badge-status { color: var(--text-muted); }