:root {
    --bd-red: #f42a41;
    --bd-red-rgb: 244, 42, 65;
    --bd-green: #006a4e;
    --bd-gold: #f7edef;
    --bd-bg: rgba(15, 15, 15, 0.95);
    --font-mono: 'Fira Code', monospace;
    --font-ui: 'Rajdhani', sans-serif;
  }
  
  /* Modal Dialog */
  .modal-dialog {
    max-width: 800px;
    margin: 30px auto;
    height: auto;
  }
  
  /* Modal Content */
  .modal-content {
    max-height: calc(100vh - 60px);
    max-width: 650px;
    overflow-y: auto;
    background: linear-gradient(to bottom, var(--bd-bg), rgba(30, 0, 0, 0.85));
    border-radius: 10px;
    color: #fff;
    font-family: var(--font-mono);
    box-shadow: 0 0 25px rgba(var(--bd-red-rgb), 0.4);
    border: 2px solid var(--bd-red);
    position: relative;
  }
  
  /* Close Button */
  .btn-close {
    color: var(--bd-red);
    background: none;
    border: 2px solid var(--bd-red);
    border-radius: 50%;
    width: 30px;
    height: 30px;
    position: absolute;
    top: 10px;
    right: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1rem;
    transition: 0.3s;
    text-shadow: 0 0 8px var(--bd-red);
  }
  .btn-close:hover {
    background-color: rgba(var(--bd-red-rgb), 0.15);
    color: #fff;
    box-shadow: 0 0 10px var(--bd-red);
  }
  
  /* Navigation Tabs */
  ul.custom-nav {
    display: flex;
    justify-content: center;
    margin: 0;
    padding: 0;
    list-style: none;
  }
  
  .nav-tabs {
    border-bottom: 2px solid var(--bd-red);
    display: flex;
    justify-content: center;
  }
  .nav-tabs .nav-link {
    color: var(--bd-red);
    font-weight: 700;
    border: 1px solid transparent;
    padding: 10px 15px;
    border-radius: 5px;
    text-shadow: 1px 1px #000;
    gap: 5px;
    transition: 0.3s;
    background-color: rgba(0, 0, 0, 0.8);
    font-family: var(--font-ui);
  }
  .nav-tabs .nav-link.active {
    background-color: rgba(var(--bd-red-rgb), 0.3);
    color: #fff;
    border: 2px solid var(--bd-red);
    border-bottom: 0;
    border-radius: 5px 5px 0 0;
    text-shadow: 2px 2px #000;
  }
  .nav-tabs .nav-link:hover {
    color: #fff;
    background-color: rgba(var(--bd-red-rgb), 0.2);
  }
  
  /* Tab Panels */
  .tab-content > .tab-pane {
    display: none;
  }
  .tab-content > .tab-pane.active {
    display: block;
    animation: fadeIn 0.5s ease-in-out;
  }
  @keyframes fadeIn {
    from { opacity: 0; transform: translateY(-10px); }
    to { opacity: 1; transform: translateY(0); }
  }
  .tab-content {
    padding: 20px 0;
    border-top: 2px solid var(--bd-red);
    max-height: calc(100vh - 200px);
    overflow-y: auto;
    overflow-x: hidden;
  }
  .tab-content::-webkit-scrollbar {
    width: 8px;
  }
  .tab-content::-webkit-scrollbar-thumb {
    background: var(--bd-red);
    border-radius: 5px;
  }
  .tab-content::-webkit-scrollbar-thumb:hover {
    background: #fff;
  }
  
  /* Headings and Meta Text */
  .challenge-name {
    font-size: 2.4em;
    font-weight: bold;
    text-align: center;
    margin-bottom: 10px;
    color: var(--bd-red);
    text-shadow: 2px 2px #000;
    font-family: var(--font-ui);
  }
  .challenge-value {
    font-size: 1.6em;
    text-align: center;
    margin-bottom: 20px;
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 10px;
    color: var(--bd-gold);
    text-shadow: 1px 1px #000;
  }
  .challenge-value i {
    font-size: 1.4em;
    color: var(--bd-red);
  }
  
  /* Descriptions */
  .challenge-desc {
    font-size: 1.05em;
    line-height: 1.6;
    font-family: var(--font-mono);
    color: #ddd;
    text-shadow: 1px 1px #000;
    margin: 20px 0;
  }
  
  /* Input Fields */
  .challenge-input {
    background: #0a0a0a;
    border: 2px solid var(--bd-red);
    border-radius: 6px;
    padding: 12px;
    color: var(--bd-red);
    font-family: var(--font-mono);
    font-size: 1.1em;
    box-shadow: inset 0 0 8px rgba(var(--bd-red-rgb), 0.3);
    transition: 0.3s ease;
  }
  .challenge-input::placeholder {
    color: rgba(var(--bd-red-rgb), 0.5);
    font-style: italic;
  }
  .challenge-input:hover,
  .challenge-input:focus {
    border-color: #fff;
    background-color: #1a0a0a;
    color: #fff;
    box-shadow: 0 0 12px rgba(var(--bd-red-rgb), 0.5);
    outline: none;
  }
  
  /* Submit Button */
  .challenge-submit {
    background: rgba(var(--bd-red-rgb), 0.25);
    color: var(--bd-red);
    border: 2px solid var(--bd-red);
    font-weight: bold;
    border-radius: 6px;
    text-shadow: 2px 2px #000;
    padding: 10px 15px;
    width: 100%;
    transition: 0.3s;
  }
  .challenge-submit:hover {
    background: rgba(var(--bd-red-rgb), 0.45);
    color: #fff;
    border-color: #fff;
    box-shadow: 0 0 10px var(--bd-red);
  }
  
  /* Submit Row */
  .submit-row {
    display: flex;
    justify-content: center;
    gap: 40px;
    margin: 20px 0;
    flex-wrap: wrap;
  }
  
  /* Alerts */
  .alert-success {
    background: rgba(0, 128, 0, 0.4);
    border: 1px solid var(--bd-green);
    color: #fff;
  }
  .alert-danger {
    background: rgba(255, 0, 0, 0.3);
    border: 1px solid var(--bd-red);
    color: #fff;
  }
  .alert-info {
    background: rgba(0, 123, 255, 0.3);
    border: 1px solid #007bff;
    color: #fff;
  }
  .alert-warning {
    background: rgba(255, 165, 0, 0.5);
    border: 1px solid var(--bd-red);
    color: #fff;
  }
  .notification-row .alert {
    margin-top: 20px;
    padding: 12px;
    border-radius: 6px;
    font-family: var(--font-ui);
    font-weight: 600;
    text-shadow: 1px 1px #000;
  }
  
  /* Author + Badge Block */
  .challenge-attribution-badge {
    background: rgba(0, 0, 0, 0.9);
    color: var(--bd-gold);
    border-radius: 20px;
    padding: 10px 15px;
    margin: 15px auto;
    max-width: 450px;
    font-family: var(--font-ui);
    font-size: 1em;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: 0 0 12px rgba(0, 0, 0, 0.4);
  }
  .attribution-label {
    color: var(--bd-red);
    font-weight: 600;
  }
  .badge-left {
    display: flex;
    gap: 10px;
    align-items: center;
  }
  .badge-right {
    color: var(--bd-gold);
    font-weight: 700;
    font-family: var(--font-mono);
    text-shadow: 0 0 5px var(--bd-gold);
  }
  
  /* Hints/Helpers */
  .hint-details {
    background: #0f0f0f;
    border: 1px solid var(--bd-red);
    border-radius: 8px;
    padding: 10px;
    box-shadow: 0 0 10px rgba(var(--bd-red-rgb), 0.3);
    transition: 0.3s;
  }
  .hint-summary {
    font-weight: bold;
    color: var(--bd-gold);
    cursor: pointer;
    margin-bottom: 5px;
    transition: 0.3s;
  }
  .hint-summary:hover {
    color: #fff;
    text-shadow: 0 0 10px var(--bd-gold);
  }
  .hint-content {
    margin-top: 10px;
    border-top: 1px solid var(--bd-gold);
    padding-top: 10px;
    font-size: 1em;
    color: var(--bd-red);
    font-family: var(--font-mono);
    line-height: 1.5;
  }