:root {
    --primary-color: #0052CC;
    --primary-hover: #0747A6;
    --success-color: #00875A;
    --warning-color: #FF8B00;
    --danger-color: #DE350B;
    --text-primary: #172B4D;
    --text-secondary: #6B778C;
    --background: #FAFBFC;
    --surface: #FFFFFF;
    --border-color: #DFE1E6;
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.06);
    --shadow-md: 0 4px 8px rgba(0, 0, 0, 0.08);
    --shadow-lg: 0 8px 16px rgba(0, 0, 0, 0.12);
    --radius: 8px;
    --transition: all 0.2s ease;
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, 'Fira Sans', 'Droid Sans', 'Helvetica Neue', sans-serif;
    background-color: var(--background);
    color: var(--text-primary);
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

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

header {
    background-color: var(--surface);
    border-bottom: 1px solid var(--border-color);
    padding: 24px 0;
    position: relative;
}

header h1 {
    font-size: 32px;
    font-weight: 700;
    color: var(--primary-color);
    margin-bottom: 8px;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 18px;
}

.language-selector {
    position: absolute;
    top: 24px;
    right: 20px;
}

#language-select {
    padding: 8px 12px;
    border: 1px solid var(--border-color);
    border-radius: var(--radius);
    background-color: var(--surface);
    color: var(--text-primary);
    font-size: 14px;
    cursor: pointer;
    transition: var(--transition);
}

#language-select:hover {
    border-color: var(--primary-color);
}

main {
    padding: 40px 0;
}

.test-control {
    text-align: center;
    margin-bottom: 40px;
}

.primary-button, .secondary-button {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 12px 24px;
    border: none;
    border-radius: var(--radius);
    font-size: 16px;
    font-weight: 500;
    cursor: pointer;
    transition: var(--transition);
}

.primary-button {
    background-color: var(--primary-color);
    color: white;
}

.primary-button:hover {
    background-color: var(--primary-hover);
    transform: translateY(-1px);
    box-shadow: var(--shadow-md);
}

.primary-button.stop {
    background-color: var(--danger-color);
}

.primary-button.stop:hover {
    background-color: #BF2600;
}

.secondary-button {
    background-color: var(--surface);
    color: var(--primary-color);
    border: 2px solid var(--primary-color);
}

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

.icon {
    width: 20px;
    height: 20px;
}

.metrics-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
    gap: 24px;
    margin-bottom: 40px;
}

.metric-card {
    background-color: var(--surface);
    border-radius: var(--radius);
    padding: 24px;
    box-shadow: var(--shadow-sm);
    transition: var(--transition);
    text-align: center;
}

.metric-card:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-2px);
}

.metric-icon {
    width: 48px;
    height: 48px;
    margin: 0 auto 16px;
    padding: 12px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
}

.metric-icon.latency {
    background-color: rgba(0, 82, 204, 0.1);
    color: var(--primary-color);
}

.metric-icon.packet-loss {
    background-color: rgba(222, 53, 11, 0.1);
    color: var(--danger-color);
}

.metric-icon.jitter {
    background-color: rgba(255, 139, 0, 0.1);
    color: var(--warning-color);
}

.metric-icon.bandwidth {
    background-color: rgba(0, 135, 90, 0.1);
    color: var(--success-color);
}

.metric-card h3 {
    font-size: 18px;
    font-weight: 500;
    margin-bottom: 12px;
    color: var(--text-secondary);
}

.metric-value {
    font-size: 36px;
    font-weight: 700;
    color: var(--text-primary);
    line-height: 1;
}

.metric-unit {
    font-size: 14px;
    color: var(--text-secondary);
    margin-top: 4px;
}

.metric-status {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    margin: 12px auto 0;
    background-color: var(--border-color);
}

.metric-status.excellent {
    background-color: var(--success-color);
}

.metric-status.good {
    background-color: #36B37E;
}

.metric-status.fair {
    background-color: var(--warning-color);
}

.metric-status.poor {
    background-color: var(--danger-color);
}

.test-status {
    background-color: var(--surface);
    border-radius: var(--radius);
    padding: 24px;
    margin-bottom: 40px;
    box-shadow: var(--shadow-sm);
}

.status-message {
    font-size: 18px;
    font-weight: 500;
    margin-bottom: 16px;
    text-align: center;
}

.progress-bar {
    width: 100%;
    height: 8px;
    background-color: var(--border-color);
    border-radius: 4px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background-color: var(--primary-color);
    width: 0%;
    transition: width 0.3s ease;
}

.results-section {
    background-color: var(--surface);
    border-radius: var(--radius);
    padding: 32px;
    margin-bottom: 40px;
    box-shadow: var(--shadow-sm);
}

.results-section h2 {
    font-size: 24px;
    margin-bottom: 24px;
    color: var(--text-primary);
}

.quality-assessment {
    text-align: center;
    margin-bottom: 32px;
}

.quality-badge {
    display: inline-block;
    padding: 8px 24px;
    border-radius: 24px;
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 12px;
}

.quality-badge.excellent {
    background-color: rgba(0, 135, 90, 0.1);
    color: var(--success-color);
}

.quality-badge.good {
    background-color: rgba(54, 179, 126, 0.1);
    color: #36B37E;
}

.quality-badge.fair {
    background-color: rgba(255, 139, 0, 0.1);
    color: var(--warning-color);
}

.quality-badge.poor {
    background-color: rgba(222, 53, 11, 0.1);
    color: var(--danger-color);
}

.quality-description {
    color: var(--text-secondary);
    font-size: 16px;
}

.recommendations {
    margin-bottom: 24px;
}

.recommendations h3 {
    font-size: 20px;
    margin-bottom: 16px;
    color: var(--text-primary);
}

.recommendations ul {
    list-style: none;
}

.recommendations li {
    padding: 8px 0;
    padding-left: 24px;
    position: relative;
    color: var(--text-secondary);
}

.recommendations li::before {
    content: "✓";
    position: absolute;
    left: 0;
    color: var(--success-color);
    font-weight: bold;
}

.info-section {
    background-color: var(--surface);
    border-radius: var(--radius);
    padding: 32px;
    box-shadow: var(--shadow-sm);
}

.info-section h2 {
    font-size: 24px;
    margin-bottom: 16px;
    color: var(--text-primary);
}

.info-section h3 {
    font-size: 20px;
    margin: 24px 0 16px;
    color: var(--text-primary);
}

.info-section p {
    color: var(--text-secondary);
    margin-bottom: 16px;
    line-height: 1.8;
}

.metrics-explanation {
    margin-top: 16px;
}

.metrics-explanation dt {
    font-weight: 600;
    color: var(--text-primary);
    margin-top: 16px;
}

.metrics-explanation dd {
    color: var(--text-secondary);
    margin-left: 0;
    margin-bottom: 16px;
    padding-left: 20px;
}

footer {
    background-color: var(--surface);
    border-top: 1px solid var(--border-color);
    padding: 24px 0;
    text-align: center;
    margin-top: 60px;
}

footer p {
    color: var(--text-secondary);
    font-size: 14px;
}

@media (max-width: 768px) {
    header h1 {
        font-size: 24px;
    }
    
    .subtitle {
        font-size: 16px;
    }
    
    .language-selector {
        position: static;
        margin-top: 16px;
    }
    
    .metrics-grid {
        grid-template-columns: 1fr;
        gap: 16px;
    }
    
    .metric-value {
        font-size: 28px;
    }
    
    .results-section,
    .info-section {
        padding: 24px;
    }
}

@media (prefers-reduced-motion: reduce) {
    * {
        transition: none !important;
        animation: none !important;
    }
}

@media (prefers-color-scheme: dark) {
    :root {
        --text-primary: #FFFFFF;
        --text-secondary: #B8C2CC;
        --background: #0D1117;
        --surface: #161B22;
        --border-color: #30363D;
    }
    
    #language-select {
        background-color: var(--surface);
        color: var(--text-primary);
    }
}