:root {
    --primary-color: #4361ee;
    --secondary-color: #3a0ca3;
    --danger-color: #f72585;
    --success-color: #4cc9f0;
    --light-color: #f8f9fa;
    --dark-color: #212529;
    --gray-color: #6c757d;
    --white: #ffffff;
    --shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    --border-radius: 8px;
}

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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background-color: #f5f7fa;
    color: var(--dark-color);
    line-height: 1.6;
}

.app-container {
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* Auth Screen */
.auth-screen {
    display: flex;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    background: linear-gradient(135deg, #4361ee, #3a0ca3);
    padding: 20px;
}

.auth-card {
    background-color: var(--white);
    padding: 2rem;
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    width: 100%;
    max-width: 500px;
    text-align: center;
}

.auth-card h1 {
    color: var(--primary-color);
    margin-bottom: 1.5rem;
    font-size: 2rem;
}

.auth-card h1 i {
    margin-right: 10px;
}

.form-group {
    margin-bottom: 1.5rem;
    text-align: left;
}

.form-group label {
    display: block;
    margin-bottom: 0.5rem;
    font-weight: 600;
    color: var(--dark-color);
}

.form-group input,
.form-group select {
    width: 100%;
    padding: 0.75rem;
    border: 1px solid #ddd;
    border-radius: var(--border-radius);
    font-size: 1rem;
    transition: border-color 0.3s;
}

.form-group input:focus,
.form-group select:focus {
    outline: none;
    border-color: var(--primary-color);
}

.primary-btn {
    background-color: var(--primary-color);
    color: white;
    border: none;
    padding: 0.75rem 1.5rem;
    border-radius: var(--border-radius);
    font-size: 1rem;
    font-weight: 600;
    cursor: pointer;
    transition: background-color 0.3s;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

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

.danger-btn {
    background-color: var(--danger-color);
    color: white;
    border: none;
    padding: 0.5rem 1rem;
    border-radius: var(--border-radius);
    font-size: 0.9rem;
    font-weight: 600;
    cursor: pointer;
    transition: background-color 0.3s;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
}

.danger-btn:hover {
    background-color: #d3166b;
}

.loader {
    border: 4px solid #f3f3f3;
    border-top: 4px solid var(--primary-color);
    border-radius: 50%;
    width: 30px;
    height: 30px;
    animation: spin 1s linear infinite;
    margin: 1rem auto;
}

@keyframes spin {
    0% { transform: rotate(0deg); }
    100% { transform: rotate(360deg); }
}

.hidden {
    display: none !important;
}

/* Classroom Screen */
.classroom-screen {
    display: flex;
    flex-direction: column;
    height: 100vh;
}

.top-bar {
    background-color: var(--white);
    padding: 1rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    box-shadow: var(--shadow);
    z-index: 10;
}

.class-info {
    display: flex;
    align-items: center;
    gap: 1rem;
}

.class-info h2 {
    color: var(--primary-color);
    font-size: 1.25rem;
}

.participant-count {
    background-color: #e9ecef;
    padding: 0.25rem 0.75rem;
    border-radius: 20px;
    display: flex;
    align-items: center;
    gap: 5px;
    font-size: 0.9rem;
}

.main-content {
    display: flex;
    flex: 1;
    overflow: hidden;
}

.video-container {
    flex: 1;
    background-color: var(--dark-color);
    position: relative;
    overflow: hidden;
}

.sidebar {
    width: 300px;
    background-color: var(--white);
    border-left: 1px solid #ddd;
    display: flex;
    flex-direction: column;
}

.sidebar-tabs {
    display: flex;
    border-bottom: 1px solid #ddd;
}

.tab-btn {
    flex: 1;
    padding: 1rem;
    background: none;
    border: none;
    cursor: pointer;
    color: var(--gray-color);
    font-size: 1.1rem;
    transition: all 0.3s;
    position: relative;
}

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

.tab-btn.active::after {
    content: '';
    position: absolute;
    bottom: 0;
    left: 0;
    width: 100%;
    height: 3px;
    background-color: var(--primary-color);
}

.tab-content {
    flex: 1;
    padding: 1rem;
    overflow-y: auto;
    display: none;
}

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

.tab-content h3 {
    margin-bottom: 1rem;
    color: var(--primary-color);
}

.participants-list {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.participant-item {
    display: flex;
    align-items: center;
    padding: 0.5rem;
    border-radius: var(--border-radius);
    background-color: #f8f9fa;
}

.participant-item i {
    margin-right: 0.5rem;
    color: var(--gray-color);
}

.participant-item.teacher {
    background-color: #e3f2fd;
}

.participant-item.teacher i {
    color: var(--primary-color);
}

.chat-messages {
    height: calc(100% - 100px);
    overflow-y: auto;
    margin-bottom: 1rem;
}

.chat-message {
    margin-bottom: 0.75rem;
    padding: 0.5rem;
    border-radius: var(--border-radius);
    background-color: #f8f9fa;
}

.chat-message.sent {
    background-color: #e3f2fd;
    margin-left: 2rem;
}

.chat-message .sender {
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 0.25rem;
}

.chat-message .time {
    font-size: 0.75rem;
    color: var(--gray-color);
    text-align: right;
}

.chat-input {
    display: flex;
    gap: 0.5rem;
}

.chat-input input {
    flex: 1;
    padding: 0.5rem;
    border: 1px solid #ddd;
    border-radius: var(--border-radius);
}

.whiteboard-container {
    height: calc(100% - 50px);
    background-color: var(--white);
    border: 1px solid #ddd;
    border-radius: var(--border-radius);
    margin-bottom: 0.5rem;
    position: relative;
}

.whiteboard-tools {
    display: flex;
    gap: 0.5rem;
    align-items: center;
}

.wb-tool {
    background: none;
    border: 1px solid #ddd;
    border-radius: 4px;
    padding: 0.5rem;
    cursor: pointer;
    transition: all 0.3s;
}

.wb-tool:hover {
    background-color: #f8f9fa;
}

.wb-tool.active {
    background-color: var(--primary-color);
    color: white;
}

.control-bar {
    background-color: var(--white);
    padding: 1rem;
    display: flex;
    justify-content: center;
    gap: 1rem;
    box-shadow: 0 -2px 5px rgba(0, 0, 0, 0.1);
}

.control-btn {
    width: 50px;
    height: 50px;
    border-radius: 50%;
    background-color: var(--primary-color);
    color: white;
    border: none;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    font-size: 1.25rem;
    transition: all 0.3s;
}

.control-btn:hover {
    background-color: var(--secondary-color);
    transform: scale(1.1);
}

.control-btn.active {
    background-color: var(--danger-color);
}

/* Modal */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 1000;
}

.modal-content {
    background-color: var(--white);
    padding: 2rem;
    border-radius: var(--border-radius);
    width: 90%;
    max-width: 500px;
    box-shadow: var(--shadow);
}

.modal-content h3 {
    margin-bottom: 1rem;
    color: var(--primary-color);
}

.token-display {
    background-color: #f8f9fa;
    padding: 1rem;
    border-radius: var(--border-radius);
    margin-bottom: 1rem;
    font-family: monospace;
    word-break: break-all;
}

.link-display {
    display: flex;
    gap: 0.5rem;
    margin-bottom: 1rem;
}

.link-display input {
    flex: 1;
    padding: 0.5rem;
    border: 1px solid #ddd;
    border-radius: var(--border-radius);
}

/* Responsive */
@media (max-width: 768px) {
    .main-content {
        flex-direction: column;
    }
    
    .sidebar {
        width: 100%;
        height: 300px;
        border-left: none;
        border-top: 1px solid #ddd;
    }
    
    .video-container {
        height: 300px;
    }
    
    .control-btn {
        width: 40px;
        height: 40px;
        font-size: 1rem;
    }
}