:root {
    --primary-color: #2c54c9;
    --secondary-color: #f8f9fa;
    --text-color: #2c3e50;
    --light-text: #7f8c8d;
    --white: #fff;
    --shadow: 0 4px 6px rgba(0, 0, 0, 0.1);
    --border-radius: 50px;
    --transition: all 0.3s cubic-bezier(0.25, 0.8, 0.25, 1);
    --clock-bg: #fff;
    --body-bg: #f8f9fa;
    --footer-text: #7f8c8d;
}

body {
    font-family: 'Noto Sans SC', sans-serif;
    background-color: var(--body-bg);
    color: var(--text-color);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 20px;
    transition: var(--transition);
    position: relative;
    padding-bottom: 80px;
}

.container {
    width: 100%;
    max-width: 600px;
    display: flex;
    flex-direction: column;
    gap: 24px;
    animation: fadeIn 1s ease-out;
}

.header {
    text-align: center;
    margin-bottom: 20px;
}

.header h1 {
    color: var(--primary-color);
    font-weight: 700;
    font-size: 2.5rem;
    margin-bottom: 10px;
    animation: slideDown 0.8s ease-out;
}

.clock-container {
    background-color: var(--clock-bg);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    padding: 40px;
    text-align: center;
    width: 100%;
    transition: var(--transition);
    border: 1px solid rgba(0, 0, 0, 0.05);
    animation: pulse 2s infinite alternate;
}

.clock-row {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 10px;
    margin-bottom: 15px;
}

.clock-label {
    font-size: 1.2rem;
    color: var(--light-text);
    width: 80px;
    text-align: right;
    transition: var(--transition);
}

.clock-display {
    font-size: clamp(2rem, 6vw, 3rem);
    color: var(--primary-color);
    font-weight: 600;
    display: flex;
    align-items: center;
    gap: 5px;
}

.clock-digit {
    display: inline-block;
    transition: transform 0.3s ease-out;
    width: 1.2em;
    text-align: center;
    position: relative;
}

.colon {
    opacity: 0.6;
    animation: blink 2s infinite;
}

.footer {
    text-align: center;
    margin-top: 40px;
    color: var(--footer-text);
    font-size: 0.9rem;
    animation: fadeIn 2s ease-out;
}

.back-button {
    position: fixed;
    top: 20px;
    left: 20px;
    background-color: var(--white);
    color: var(--primary-color);
    border: none;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    box-shadow: var(--shadow);
    z-index: 100;
    transition: var(--transition);
}

.back-button:hover {
    transform: scale(1.1);
    background-color: var(--primary-color);
    color: var(--white);
}

/* 动画关键帧 */
@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

@keyframes slideDown {
    from { 
        opacity: 0;
        transform: translateY(-30px);
    }
    to { 
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes pulse {
    0% { transform: scale(1); }
    100% { transform: scale(1.01); }
}

@keyframes blink {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.3; }
}

@keyframes bounce {
    0%, 100% { transform: translateX(-50%) translateY(0); }
    50% { transform: translateX(-50%) translateY(-5px); }
}

@keyframes digitFlip {
    0% { transform: rotateX(0deg); }
    50% { transform: rotateX(90deg); }
    100% { transform: rotateX(0deg); }
}

@media (min-width: 768px) {
    .back-button {
        position: absolute;
        top: 20px;
        left: 20px;
    }
    
    .back-button:hover {
        transform: translateX(-5px) scale(1.1);
    }
}