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

:root {
    --primary-color: #6366f1;
    --primary-dark: #4f46e5;
    --primary-light: #818cf8;
    --secondary-color: #8b5cf6;
    --success-color: #10b981;
    --background: #0f172a;
    --card-bg: #1e293b;
    --card-hover: #334155;
    --text-primary: #f1f5f9;
    --text-secondary: #cbd5e1;
    --text-muted: #94a3b8;
    --border-color: #334155;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow: 0 4px 6px -1px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
    --shadow-xl: 0 20px 25px -5px rgb(0 0 0 / 0.1);
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol";
    background: linear-gradient(135deg, #0f172a 0%, #1e293b 100%);
    color: var(--text-primary);
    min-height: 100vh;
    padding: 20px;
    line-height: 1.6;
}

/* 返回按钮 */
.back-btn {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    padding: 8px 14px;
    background: rgba(30, 41, 59, 0.6);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    font-size: 0.875rem;
    transition: all 0.3s ease;
    margin-bottom: 20px;
}

.back-btn:hover {
    background: var(--card-bg);
    border-color: var(--primary-light);
    color: var(--primary-light);
}

.back-icon {
    font-size: 1rem;
    transition: transform 0.3s ease;
}

.back-btn:hover .back-icon {
    transform: translateX(-3px);
}

.back-text {
    display: inline;
}

.container {
    max-width: 600px;
    margin: 0 auto;
}

header {
    text-align: center;
    margin-bottom: 40px;
    animation: fadeInDown 0.6s ease-out;
}

header h1 {
    font-size: 2.5rem;
    font-weight: 700;
    margin-bottom: 10px;
    background: linear-gradient(135deg, var(--primary-light), var(--secondary-color));
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.subtitle {
    color: var(--text-secondary);
    font-size: 1.1rem;
}

.calculator-card {
    background: var(--card-bg);
    border-radius: 20px;
    padding: 30px;
    box-shadow: var(--shadow-xl);
    border: 1px solid var(--border-color);
    margin-bottom: 30px;
    animation: fadeInUp 0.6s ease-out;
}

.input-group {
    margin-bottom: 25px;
}

.input-group label {
    display: flex;
    align-items: center;
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 10px;
    color: var(--text-primary);
}

.input-group .icon {
    margin-right: 8px;
    font-size: 1.2rem;
}

input[type="time"],
input[type="number"] {
    width: 100%;
    padding: 14px 18px;
    font-size: 1.1rem;
    border: 2px solid var(--border-color);
    border-radius: 12px;
    background: var(--background);
    color: var(--text-primary);
    transition: all 0.3s ease;
    font-family: inherit;
}

input[type="time"]:focus,
input[type="number"]:focus {
    outline: none;
    border-color: var(--primary-color);
    box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.1);
}

input[type="time"]::-webkit-calendar-picker-indicator {
    filter: invert(1);
    cursor: pointer;
}

.hours-input-wrapper {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.quick-buttons {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 8px;
}

.quick-btn {
    padding: 10px;
    border: 2px solid var(--border-color);
    border-radius: 10px;
    background: var(--background);
    color: var(--text-secondary);
    font-size: 0.95rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.3s ease;
}

.quick-btn:hover {
    background: var(--card-hover);
    border-color: var(--primary-light);
}

.quick-btn.active {
    background: var(--primary-color);
    border-color: var(--primary-color);
    color: white;
}

.calculate-btn {
    width: 100%;
    padding: 16px;
    font-size: 1.1rem;
    font-weight: 600;
    color: white;
    background: linear-gradient(135deg, var(--primary-color), var(--secondary-color));
    border: none;
    border-radius: 12px;
    cursor: pointer;
    transition: all 0.3s ease;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    box-shadow: var(--shadow-lg);
}

.calculate-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-xl);
}

.calculate-btn:active {
    transform: translateY(0);
}

.btn-icon {
    font-size: 1.3rem;
}

.result {
    margin-top: 30px;
    padding: 25px;
    background: linear-gradient(135deg, rgba(99, 102, 241, 0.1), rgba(139, 92, 246, 0.1));
    border-radius: 16px;
    border: 2px solid var(--primary-color);
    animation: slideIn 0.4s ease-out;
}

.result-header {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 1rem;
    color: var(--text-secondary);
    margin-bottom: 12px;
}

.result-time {
    font-size: 3rem;
    font-weight: 700;
    color: var(--primary-light);
    text-align: center;
    margin: 15px 0;
    text-shadow: 0 0 20px rgba(99, 102, 241, 0.3);
}

.result-detail {
    text-align: center;
    color: var(--text-secondary);
    font-size: 1rem;
    margin-bottom: 15px;
}

.sleep-tip {
    background: rgba(16, 185, 129, 0.1);
    border: 1px solid var(--success-color);
    border-radius: 10px;
    padding: 12px 16px;
    color: var(--success-color);
    font-size: 0.95rem;
    margin-top: 15px;
}

.info-cards {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
    gap: 15px;
    margin-bottom: 30px;
    animation: fadeInUp 0.6s ease-out 0.2s both;
}

.info-card {
    background: var(--card-bg);
    border: 1px solid var(--border-color);
    border-radius: 16px;
    padding: 20px;
    text-align: center;
    transition: all 0.3s ease;
}

.info-card:hover {
    transform: translateY(-5px);
    box-shadow: var(--shadow-lg);
    border-color: var(--primary-color);
}

.info-icon {
    font-size: 2rem;
    margin-bottom: 10px;
}

.info-card h3 {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: 8px;
    color: var(--text-primary);
}

.info-card p {
    font-size: 0.9rem;
    color: var(--text-muted);
    line-height: 1.5;
}

footer {
    text-align: center;
    padding: 20px;
    color: var(--text-secondary);
    animation: fadeIn 0.6s ease-out 0.4s both;
}

/* 动画 */
@keyframes fadeInDown {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeInUp {
    from {
        opacity: 0;
        transform: translateY(20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

@keyframes fadeIn {
    from {
        opacity: 0;
    }
    to {
        opacity: 1;
    }
}

@keyframes slideIn {
    from {
        opacity: 0;
        transform: scale(0.95);
    }
    to {
        opacity: 1;
        transform: scale(1);
    }
}

/* 手机端适配 */
@media (max-width: 640px) {
    body {
        padding: 15px;
    }

    .back-btn {
        padding: 6px 12px;
        font-size: 0.8rem;
        margin-bottom: 15px;
    }

    .back-icon {
        font-size: 0.9rem;
    }

    header h1 {
        font-size: 2rem;
    }

    .subtitle {
        font-size: 1rem;
    }

    .calculator-card {
        padding: 20px;
    }

    .result-time {
        font-size: 2.5rem;
    }

    .info-cards {
        grid-template-columns: 1fr;
    }

    .quick-buttons {
        grid-template-columns: repeat(4, 1fr);
        gap: 6px;
    }

    .quick-btn {
        padding: 8px;
        font-size: 0.9rem;
    }
}

@media (max-width: 400px) {
    header h1 {
        font-size: 1.75rem;
    }

    .calculator-card {
        padding: 18px;
    }

    .result-time {
        font-size: 2rem;
    }
}