body {
    margin: 0;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

.main-content {
    flex: 1;
    width: 100%;
    max-width: 1920px;
    margin: 0 auto;
    padding-left: 1rem;
    padding-right: 1rem;
}

.header-gradient {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    width: 100%;
}

.tab-active {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(102, 126, 234, 0.4);
}

.tab-inactive {
    background: #f8fafc;
    color: #64748b;
    border: 1px solid #e2e8f0;
}

.dropdown-enter {
    animation: slideDown 0.3s ease-out;
}

@keyframes slideDown {
    from { opacity: 0; transform: translateY(-10px); }
    to { opacity: 1; transform: translateY(0); }
}

.preview-box {
    transition: all 0.5s ease-in-out;
    border: 2px dashed #667eea;
    background: #f8fafc;
    position: relative;
}

.resolution-item {
    background: #ffffff;
    color: #1f2937;
    transition: all 0.2s ease-in-out;
}

.resolution-item:hover {
    background: #667eea;
    color: white;
    transform: translateX(4px);
    box-shadow: 0 2px 8px rgba(102, 126, 234, 0.3);
}

#preview-box { position: relative; }

#preview-default {
    position: absolute;
    top: 0; left: 0;
    width: 100%; height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
}

#preview-iframe {
    position: absolute;
    top: 0; left: 0;
    width: 100%; height: 100%;
    border: none;
    display: none;
}

#url-input::placeholder { color: #6b7280; }

footer {
    width: 100%;
    background: #1f2937;
    margin-top: auto;
}

#resolution-dropdown {
    position: absolute;
    top: 100%;
    left: 0; right: 0;
    z-index: 50;
    background: white;
    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.1);
    border-radius: 0.5rem;
}

@media (max-width: 768px) {
    .main-content {
        padding-left: 0.5rem;
        padding-right: 0.5rem;
    }
    #url-input { width: 100%; }
    .header-menu { flex-wrap: wrap; gap: 0.5rem; }
    .device-buttons { flex-wrap: wrap; gap: 0.5rem; }
}