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

body {
    font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

.main-header {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 10px 30px;
    text-align: center;
}

.main-header h1 {
    font-size: 2.5em;
    margin-bottom: 10px;
    font-weight: 700;
}

.main-header p {
    font-size: 1.1em;
    opacity: 0.95;
}

.tab-navigation {
    display: flex;
    background: #f8f9fa;
    padding: 0;
    border-bottom: 3px solid #e9ecef;
    position: sticky;
    top: 0;
    z-index: 100;
    overflow-x: auto;
    overflow-y: hidden;
    -webkit-overflow-scrolling: touch;
    scrollbar-width: thin;
    scrollbar-color: #667eea #f8f9fa;
}

.tab-navigation::-webkit-scrollbar {
    height: 4px;
}

.tab-navigation::-webkit-scrollbar-track {
    background: #f8f9fa;
}

.tab-navigation::-webkit-scrollbar-thumb {
    background: #667eea;
    border-radius: 2px;
}

.tab-btn {
    flex: 1 0 auto;
    padding: 20px 25px;
    background: transparent;
    border: none;
    font-size: 1em;
    font-weight: 600;
    color: #495057;
    cursor: pointer;
    transition: all 0.3s ease;
    position: relative;
    white-space: nowrap;
    min-width: 200px;
}

.tab-btn:hover {
    background: rgba(102, 126, 234, 0.1);
    color: #667eea;
}

.tab-btn.active {
    background: white;
    color: #667eea;
}

.tab-btn.active::after {
    content: '';
    position: absolute;
    bottom: -3px;
    left: 0;
    right: 0;
    height: 3px;
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
}

.content-area {
    background: #f8f9fa;
    min-height: calc(100vh - 250px);
    position: relative;
}

#content-frame {
    width: 100%;
    min-height: calc(100vh - 250px);
    border: none;
    background: white;
    transition: opacity 0.3s ease;
}

/* Responsive Design */
@media (max-width: 1024px) {
    .tab-btn {
        min-width: 180px;
        padding: 18px 20px;
    }
}

@media (max-width: 768px) {
    body {
        padding: 0;
    }

    .main-header h1 {
        font-size: 1.8em;
    }

    .main-header p {
        font-size: 0.95em;
    }

    .main-header {
        padding: 20px 15px;
    }

    .tab-navigation {
        justify-content: flex-start;
    }

    .tab-btn {
        flex: 0 0 auto;
        padding: 15px 18px;
        font-size: 0.9em;
        min-width: 160px;
    }

    .content-area {
        min-height: calc(100vh - 200px);
    }

    #content-frame {
        min-height: calc(100vh - 200px);
    }
}

@media (max-width: 480px) {
    .main-header h1 {
        font-size: 1.4em;
        margin-bottom: 5px;
    }

    .main-header p {
        font-size: 0.85em;
    }

    .main-header {
        padding: 15px 10px;
    }

    .tab-btn {
        padding: 12px 15px;
        font-size: 0.8em;
        min-width: 140px;
    }

    .main-footer {
        padding: 15px 10px;
        font-size: 0.85em;
    }

    .content-area {
        min-height: calc(100vh - 180px);
    }

    #content-frame {
        min-height: calc(100vh - 180px);
    }
}

@media (max-width: 360px) {
    .main-header h1 {
        font-size: 1.2em;
    }

    .main-header p {
        font-size: 0.8em;
    }

    .tab-btn {
        padding: 10px 12px;
        font-size: 0.75em;
        min-width: 120px;
    }
}

/* Loading animation */
@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

.content-area {
    animation: fadeIn 0.5s ease-in;
}

.main-footer {
    background: #2d3748;
    color: white;
    text-align: center;
    padding: 20px;
    font-size: 0.95em;
}