:root {
    --background-color: #121212;
    --card-background-color: rgba(30, 30, 30, 0.85); /* 增加透明度以透出背景 */
    --primary-text-color: #e0e0e0;
    --secondary-text-color: #b0b0b0;
    --accent-color: #007bff; /* 主入口/默认按钮 */
    --accent-hover-color: #0056b3;
    --success-color: #28a745; /* 备用入口按钮 */
    --backup-hover-color: #218838;
    --error-color: #dc3545;
    --border-color: rgba(80, 80, 80, 0.5);
    /* --- 关键修改：使用系统字体方案 --- */
    --font-family: -apple-system, BlinkMacSystemFont, "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei UI", "Microsoft YaHei", "Segoe UI", Roboto, "Helvetica Neue", Helvetica, Arial, sans-serif;
    --border-radius: 12px;
    --box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
}

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

html, body {
    height: 100%;
}

body {
    font-family: var(--font-family);
    background-color: var(--background-color); /* Fallback color */
    color: var(--primary-text-color);
    display: flex;
    justify-content: center;
    align-items: center;
    overflow: hidden;
    /* --- 关键修改：恢复背景图，并叠加一层暗色网格 --- */
    background-image: radial-gradient(circle at 1px 1px, rgba(0,0,0,0.4) 1px, transparent 0), url('https://cn.bing.com/th?id=OHR.PalouseWA_ZH-CN2552273820_1920x1080.jpg');
    background-size: 20px 20px, cover;
    background-position: center;
    opacity: 0;
    animation: fadeIn 0.8s ease-in-out forwards;
}

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

#app-root {
    width: 100%;
    max-width: 420px;
    padding: 20px;
}

.card {
    background-color: var(--card-background-color);
    backdrop-filter: blur(10px);
    -webkit-backdrop-filter: blur(10px);
    border-radius: var(--border-radius);
    padding: 2.5rem;
    border: 1px solid var(--border-color);
    box-shadow: var(--box-shadow);
    text-align: center;
    transition: all 0.3s ease-in-out;
}

.card.hidden {
    display: none;
}

.card-header h2 {
    font-size: 2rem;
    font-weight: 700;
    margin-bottom: 0.75rem;
}

.card-header p {
    color: var(--secondary-text-color);
    font-size: 1rem;
    line-height: 1.6;
    margin-bottom: 2rem;
}

.verification-form {
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
}

.verification-question {
    font-size: 3rem;
    font-weight: 700;
    letter-spacing: 0.2rem;
    color: var(--primary-text-color);
    user-select: none;
}

.input-field {
    font-family: inherit;
    font-size: 1.5rem;
    padding: 1rem;
    background-color: rgba(0,0,0,0.2);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    color: var(--primary-text-color);
    text-align: center;
    width: 100%;
    transition: border-color 0.2s, box-shadow 0.2s;
}

.input-field::placeholder {
    color: #6c757d;
}

.input-field:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 0 3px rgba(0, 123, 255, 0.25);
}

.button {
    font-family: inherit;
    font-size: 1.1rem;
    font-weight: 500;
    padding: 1rem 1.5rem;
    /* 修复：添加默认背景（蓝色），确保验证按钮有色 */
    background-color: var(--accent-color);
    color: white;
    border: none;
    border-radius: 8px;
    cursor: pointer;
    transition: background-color 0.2s ease, transform 0.1s ease;
    text-decoration: none;
    display: inline-block;
    margin: 0.5rem;
    width: auto;
}

.button:hover {
    /* 修复：通用 hover（默认深蓝），子类覆盖 */
    background-color: var(--accent-hover-color);
    transform: scale(1.02);
}

.button:active {
    transform: scale(0.98);
}

.button:disabled {
    background-color: #555;
    cursor: not-allowed;
    opacity: 0.7;
}

/* 主入口按钮（蓝色，覆盖默认） */
.main-button {
    background-color: var(--accent-color);
}

.main-button:hover {
    background-color: var(--accent-hover-color);
}

/* 备用入口按钮（绿色，覆盖默认） */
.backup-button {
    background-color: var(--success-color);
}

.backup-button:hover {
    background-color: var(--backup-hover-color);
}

#feedbackMessage {
    margin-top: 1.5rem;
    min-height: 1.2rem;
    font-weight: 500;
    transition: color 0.3s;
}

#feedbackMessage.success { color: var(--success-color); }
#feedbackMessage.error { color: var(--error-color); }
#feedbackMessage.info { color: var(--secondary-text-color); }

#urlList {
    display: flex;
    flex-direction: column;
    gap: 1rem;
    margin-top: 1.5rem;
    /* 备用入口分隔样式 */
}

#urlList > div[style*="border-top"] {
    padding-top: 1rem;
    border-top: 1px solid var(--border-color);
}

.footer {
    position: fixed;
    bottom: 20px;
    left: 50%;
    transform: translateX(-50%);
    font-size: 0.85rem;
    color: rgba(255, 255, 255, 0.6);
    text-shadow: 0 1px 2px rgba(0,0,0,0.5);
    z-index: 10;
}

.footer a {
    color: inherit;
    text-decoration: none;
    transition: color 0.3s ease;
}

.footer a:hover {
    color: rgba(255, 255, 1);
}

/* 移动端优化 */
@media (max-width: 480px) {
    #app-root {
        padding: 10px;
    }
    .card {
        padding: 1.5rem;
    }
    .verification-question {
        font-size: 2.5rem;
    }
    #urlList {
        gap: 0.75rem;
    }
    .button {
        width: 100%; /* 按钮全宽 */
        margin: 0.25rem 0;
    }
}