:root {
    --bg-color: #f4f4f5;
    --text-color: #18181b;
    --card-bg: #ffffff;
    --primary: #2563eb;
    --danger: #d9363e;
    /* Improved contrast for accessibility */
}

body {
    font-family: system-ui, -apple-system, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-color);
    margin: 0;
    padding: 2rem;
    line-height: 1.5;
}

.container {
    max-width: 1000px;
    margin: 0 auto;
}

h1 {
    margin-bottom: 0.5rem;
}

.subtitle {
    margin-top: 0;
    color: #52525b;
}

.controls {
    display: flex;
    gap: 1rem;
    margin: 2rem 0;
    align-items: center;
}

button {
    padding: 0.6rem 1.2rem;
    background: var(--primary);
    color: white;
    border: none;
    border-radius: 6px;
    font-weight: 600;
    cursor: pointer;
    font-size: 1rem;
}

button:disabled {
    background: #94a3b8;
    cursor: not-allowed;
}

button:hover:not(:disabled) {
    background: #1d4ed8;
}

.status-indicator {
    padding: 0.5rem 1rem;
    border-radius: 6px;
    background: #e4e4e7;
    font-family: monospace;
}

.jank-test {
    margin: 2rem 0;
    padding: 1rem;
    background: var(--card-bg);
    border-radius: 8px;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    display: flex;
    align-items: center;
    gap: 1rem;
}

.spinner {
    width: 30px;
    height: 30px;
    border: 4px solid #f3f3f3;
    border-top: 4px solid #3498db;
    border-radius: 50%;
    /* animation: spin 1s linear infinite; removed to use JS for blocking demo */
    box-shadow: 0 0 10px #ef4444aa;
    margin-right: 10px;
    display: inline-block;
}

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

.spinner-label {
    font-family: monospace;
    font-size: 1.2em;
    color: var(--danger);
    margin-left: 10px;
}

.chart-container {
    background: var(--card-bg);
    border-radius: 8px;
    box-shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
    padding: 1rem;
    height: 400px;
    position: relative;
}