:root {
    --primary-color: #4285f4;
    --secondary-color: #34a853;
    --danger-color: #ea4335;
    --warning-color: #fbbc05;
    --background-color: #f8f9fa;
    --text-color: #202124;
    --purple-color: #800080;
}

body {
    font-family: 'Roboto', 'Helvetica Neue', sans-serif;
    background-color: var(--background-color);
    color: var(--text-color);
    display: flex;
    flex-direction: column;
    align-items: center;
    /* justify-content: center; <-- Removed for fixed header layout */
    min-height: 100vh;
    margin: 0;
    /* padding: 20px; <-- Remove overall padding */
    /* padding-top is handled by header.css */
    padding-left: 20px;
    padding-right: 20px;
    padding-bottom: 20px;
    box-sizing: border-box;
    transition: background-color 0.3s ease;
}

.hidden {
    /* 非表示用クラス */
    display: none;
}

@media (max-width: 500px) {
    .timer-display {
        font-size: 48px;
    }

    button {
        padding: 10px 16px;
        font-size: 14px;
    }

    .start-btn,
    .stop-btn {
        padding: 12px 20px;
        font-size: 16px;
    }
}