:root {
    /* Color Palette */
    --bg-color: #0d1117;
    --surface-color: #161b22;
    --surface-color-hover: #21262d;
    --text-primary: #e6edf3;
    --text-secondary: #8b949e;
    --border-color: #30363d;
    
    /* Accents */
    --primary-color: #58a6ff;
    --primary-color-hover: #3182ce;
    --danger-color: #f85149;
    --success-color: #2ea043;
    --warning-color: #d29922;
    
    /* Typography */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
    
    /* Utilities */
    --border-radius: 12px;
    --transition-speed: 0.2s;
    --box-shadow: 0 8px 24px rgba(0, 0, 0, 0.2);
}

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

body {
    font-family: var(--font-family);
    background-color: var(--bg-color);
    color: var(--text-primary);
    line-height: 1.5;
    min-height: 100vh;
}

/* Typography */
h1, h2, h3, h4, h5, h6 {
    font-weight: 600;
}

/* Container */
.app-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 20px;
}

/* Header */
.app-header {
    padding: 30px 0;
    margin-bottom: 20px;
    border-bottom: 1px solid var(--border-color);
}

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

.logo-wrapper {
    display: flex;
    align-items: center;
    gap: 15px;
}

.logo-icon {
    width: 40px;
    height: 40px;
    background: linear-gradient(135deg, var(--primary-color), #8a2be2);
    border-radius: 10px;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    font-size: 20px;
    color: white;
    box-shadow: 0 4px 12px rgba(88, 166, 255, 0.3);
}

.logo-wrapper h1 {
    font-size: 24px;
    letter-spacing: -0.5px;
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 10px 20px;
    border-radius: 8px;
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-speed) ease;
    border: none;
    font-family: inherit;
}

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

.btn-primary:hover {
    background-color: var(--primary-color-hover);
    transform: translateY(-1px);
    box-shadow: 0 4px 12px rgba(88, 166, 255, 0.2);
}

.btn-secondary {
    background-color: transparent;
    color: var(--text-primary);
    border: 1px solid var(--border-color);
}

.btn-secondary:hover {
    background-color: var(--surface-color-hover);
}

.icon-btn {
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    padding: 6px;
    border-radius: 6px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all var(--transition-speed);
}

.icon-btn:hover {
    background-color: var(--bg-color);
    color: var(--text-primary);
}

.icon-btn.edit-btn:hover {
    color: var(--primary-color);
}

.icon-btn.delete-btn:hover {
    color: var(--danger-color);
}

/* Dashboard */
.dashboard {
    padding-bottom: 50px;
}

/* Stats Overview */
.stats-overview {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(200px, 1fr));
    gap: 20px;
    margin-bottom: 30px;
}

.stat-card {
    background-color: var(--surface-color);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 20px;
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.stat-title {
    font-size: 14px;
    color: var(--text-secondary);
    font-weight: 500;
}

.stat-value {
    font-size: 32px;
    font-weight: 700;
}

/* Students Grid */
.students-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
    gap: 20px;
}

/* Student Card */
.student-card {
    background-color: var(--surface-color);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 20px;
    transition: transform var(--transition-speed), box-shadow var(--transition-speed);
    display: flex;
    flex-direction: column;
    gap: 20px;
    position: relative;
    overflow: hidden;
}

.student-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 4px;
    background: linear-gradient(90deg, var(--primary-color), transparent);
    opacity: 0;
    transition: opacity var(--transition-speed);
}

.student-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--box-shadow);
    border-color: #484f58;
}

.student-card:hover::before {
    opacity: 1;
}

.card-header {
    display: flex;
    align-items: center;
    gap: 15px;
}

.student-avatar {
    width: 48px;
    height: 48px;
    border-radius: 50%;
    background-color: var(--surface-color-hover);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 20px;
    font-weight: bold;
    color: var(--text-secondary);
    border: 1px solid var(--border-color);
}

.student-info .name {
    font-size: 18px;
    margin-bottom: 4px;
}

.student-info .id {
    font-size: 12px;
    color: var(--text-secondary);
    font-family: monospace;
}

.card-body {
    flex-grow: 1;
}

.points-display {
    display: flex;
    justify-content: space-between;
    align-items: center;
    background-color: rgba(0,0,0,0.2);
    padding: 15px;
    border-radius: 8px;
}

.points-label {
    font-size: 14px;
    color: var(--text-secondary);
}

.points-value {
    font-size: 24px;
    font-weight: bold;
    color: var(--primary-color);
}

.points-value.negative {
    color: var(--danger-color);
}
.points-value.positive {
    color: var(--success-color);
}

.card-footer {
    display: flex;
    justify-content: stretch;
}

.action-btn {
    width: 100%;
    padding: 12px;
    background-color: var(--surface-color-hover);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    border-radius: 8px;
    cursor: pointer;
    font-weight: 500;
    transition: all var(--transition-speed);
}

.action-btn:hover {
    background-color: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
}

/* Modals */
.modal-backdrop {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.7);
    backdrop-filter: blur(4px);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    opacity: 1;
    transition: opacity 0.3s ease;
}

.modal-backdrop.hidden {
    opacity: 0;
    pointer-events: none;
}

.modal {
    background-color: var(--surface-color);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    width: 100%;
    max-width: 500px;
    box-shadow: 0 20px 40px rgba(0,0,0,0.4);
    transform: translateY(0) scale(1);
    transition: transform 0.3s cubic-bezier(0.175, 0.885, 0.32, 1.275);
}

.modal-backdrop.hidden .modal {
    transform: translateY(20px) scale(0.95);
}

.modal-header {
    padding: 20px 24px;
    border-bottom: 1px solid var(--border-color);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.modal-header h2 {
    font-size: 18px;
    margin: 0;
}

.close-modal-btn {
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 24px;
    cursor: pointer;
    line-height: 1;
    transition: color 0.2s;
}

.close-modal-btn:hover {
    color: var(--text-primary);
}

.modal-body {
    padding: 24px;
    max-height: 60vh;
    overflow-y: auto;
}

.modal-footer {
    padding: 20px 24px;
    border-top: 1px solid var(--border-color);
    display: flex;
    justify-content: flex-end;
    gap: 12px;
}

/* Forms */
.form-group, .input-group {
    margin-bottom: 20px;
}

.form-group label, .input-group label {
    display: block;
    margin-bottom: 8px;
    font-weight: 500;
    font-size: 14px;
    color: var(--text-secondary);
}

input[type="text"],
input[type="number"] {
    width: 100%;
    padding: 12px;
    background-color: var(--bg-color);
    border: 1px solid var(--border-color);
    color: var(--text-primary);
    border-radius: 8px;
    font-size: 14px;
    font-family: inherit;
    transition: border-color var(--transition-speed);
}

input[type="text"]:focus,
input[type="number"]:focus {
    outline: none;
    border-color: var(--primary-color);
}

/* Action Modal Specifics */
.target-student {
    margin-bottom: 20px;
    font-size: 14px;
    padding: 12px;
    background-color: var(--surface-color-hover);
    border-radius: 8px;
    border-left: 3px solid var(--primary-color);
}

.target-student span {
    font-weight: 600;
    color: var(--text-primary);
}

.action-tabs {
    display: flex;
    border-bottom: 1px solid var(--border-color);
    margin-bottom: 20px;
}

.tab-btn {
    flex: 1;
    padding: 12px;
    background: none;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    font-weight: 500;
    font-size: 14px;
    border-bottom: 2px solid transparent;
    transition: all var(--transition-speed);
}

.tab-btn:hover {
    color: var(--text-primary);
}

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

.tab-content {
    display: none;
    animation: fadeIn 0.3s ease;
}

.tab-content.active {
    display: block;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(5px); }
    to { opacity: 1; transform: translateY(0); }
}

/* Custom Radio Buttons for Categories */
.category-options {
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.category-radio {
    position: relative;
    cursor: pointer;
}

.category-radio input[type="radio"] {
    position: absolute;
    opacity: 0;
    cursor: pointer;
}

.radio-label {
    display: block;
    padding: 12px 16px;
    background-color: var(--bg-color);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    font-size: 14px;
    transition: all var(--transition-speed);
}

.category-radio:hover .radio-label {
    border-color: #484f58;
}

.category-radio input[type="radio"]:checked ~ .radio-label {
    background-color: rgba(248, 81, 73, 0.1);
    border-color: var(--danger-color);
    color: var(--danger-color);
}

.category-radio.positive input[type="radio"]:checked ~ .radio-label {
    background-color: rgba(46, 160, 67, 0.1);
    border-color: var(--success-color);
    color: var(--success-color);
}

/* Toast System */
.toast-container {
    position: fixed;
    bottom: 20px;
    right: 20px;
    z-index: 9999;
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.toast {
    padding: 12px 20px;
    background-color: var(--surface-color);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    color: var(--text-primary);
    box-shadow: 0 4px 12px rgba(0,0,0,0.3);
    font-size: 14px;
    display: flex;
    align-items: center;
    gap: 10px;
    transform: translateX(120%);
    animation: slideIn 0.3s forwards, fadeOut 0.3s forwards 2.7s;
}

.toast.success { border-left: 4px solid var(--success-color); }
.toast.error { border-left: 4px solid var(--danger-color); }
.toast.info { border-left: 4px solid var(--primary-color); }

@keyframes slideIn {
    to { transform: translateX(0); }
}

@keyframes fadeOut {
    to { opacity: 0; visibility: hidden; }
}

/* Leaderboards */
.leaderboards-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 20px;
    margin-bottom: 30px;
}

.leaderboard-card {
    background-color: var(--surface-color);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 20px;
}

.leaderboard-card h3 {
    margin-bottom: 15px;
    border-bottom: 1px solid var(--border-color);
    padding-bottom: 10px;
}

.leaderboard-list {
    list-style: none;
    margin: 0;
    padding: 0;
}

.leaderboard-list li {
    display: flex;
    justify-content: space-between;
    padding: 10px 0;
    border-bottom: 1px solid rgba(255, 255, 255, 0.05);
    font-size: 15px;
}

.leaderboard-list li:last-child {
    border-bottom: none;
}

.leaderboard-name {
    font-weight: 500;
}

.leaderboard-points {
    color: var(--primary-color);
    font-weight: 600;
}

/* Responsive */
@media (max-width: 768px) {
    .header-content {
        flex-direction: column;
        gap: 15px;
        align-items: flex-start;
    }
    
    .logo-wrapper h1 {
        font-size: 20px;
    }
    
    .students-grid {
        grid-template-columns: 1fr;
    }
}

/* PIN Lock Screen */
.pin-backdrop {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: var(--bg-color);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 2000;
}

.pin-modal {
    background-color: var(--surface-color);
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    padding: 40px;
    width: 100%;
    max-width: 400px;
    box-shadow: 0 20px 40px rgba(0,0,0,0.5);
}