@import url('https://fonts.googleapis.com/css2?family=Inter:wght@400;500;700&display=swap');

:root {
    --primary-color: #3F51B5;
    --primary-dark: #303F9F;
    --accent-color: #448AFF;
    --background-color: #F8F9FA;
    --card-color: #FFFFFF;
    --text-color: #212121;
    --text-secondary-color: #6c757d;
    --border-color: #dee2e6;
    --error-color: #D32F2F;
    --error-dark: #C62828;
    --success-color: #28a745;
    /* ==================== 新增颜色变量 ==================== */
    --warning-color: #FFFF00; /* 纯黄色 */
    --warning-dark: #F0E600; /* 黄色的悬停加深效果 */

    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", "Microsoft YaHei", "微软雅黑", Arial, sans-serif;
    --border-radius: 8px;
    --shadow: 0 4px 6px -1px rgba(0, 0, 0, 0.1), 0 2px 4px -2px rgba(0, 0, 0, 0.1);
}

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

body {
    font-family: var(--font-family);
    background-color: var(--background-color);
    color: var(--text-color);
    display: flex;
    justify-content: center;
    padding: 20px;
    min-height: 100vh;
}

.app-container {
    width: 100%;
    max-width: 650px;
    display: flex;
    flex-direction: column;
    gap: 25px;
}

/* --- Header & Footer --- */
.app-header, .app-footer, .app-nav { text-align: center; }
.app-header h1 { font-size: 2rem; font-weight: 700; color: var(--primary-color); }
.app-header .subtitle { font-size: 1rem; color: var(--text-secondary-color); margin-top: 4px; }
.app-footer p { font-size: 0.875rem; color: #adb5bd; }

/* --- Buttons --- */
.btn {
    display: inline-block;
    font-family: inherit;
    font-size: 1rem;
    font-weight: 500;
    text-align: center;
    text-decoration: none;
    padding: 12px 24px;
    border: none;
    border-radius: var(--border-radius);
    cursor: pointer;
    transition: all 0.2s ease-in-out;
    user-select: none;
}
.btn.primary { background-color: var(--primary-color); color: white; }
.btn.primary:hover { background-color: var(--primary-dark); transform: translateY(-2px); box-shadow: var(--shadow); }
.btn.secondary { background-color: #e9ecef; color: var(--text-color); }
.btn.secondary:hover { background-color: #ced4da; }
.btn.danger { background-color: var(--error-color); color: white; }
.btn.danger:hover { background-color: var(--error-dark); }
.btn:disabled { background-color: #ced4da; cursor: not-allowed; transform: none; box-shadow: none; }

/* ==================== 新增按钮样式 ==================== */
.btn.warning {
    background-color: var(--warning-color);
    color: var(--text-color); /* 黄色背景必须用深色文字 */
    font-weight: 600; /* 加粗以增加清晰度 */
}
.btn.warning:hover {
    background-color: var(--warning-dark);
}


.button-group { display: flex; gap: 15px; }
.button-group .btn { flex: 1; }

/* 底部导航栏布局调整 */
.app-nav {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 15px;
}
.app-nav .btn, .app-nav a {
    /* flex: 1; (已移除) */
}


/* --- Cards & Forms --- */
.card {
    background-color: var(--card-color);
    border-radius: var(--border-radius);
    box-shadow: var(--shadow);
    overflow: hidden;
}
.card-header, .card-content, .card-footer { padding: 20px 25px; }
.card-header { border-bottom: 1px solid var(--border-color); }
.card-header h2 { font-size: 1.25rem; }
.card-content { display: flex; flex-direction: column; gap: 20px; }
.card-footer { border-top: 1px solid var(--border-color); background-color: #f8f9fa; }

.form-group { display: flex; flex-direction: column; gap: 8px; }
label { font-weight: 500; color: var(--text-secondary-color); }
input, select {
    font-family: inherit;
    font-size: 1rem;
    padding: 12px;
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    background-color: #F8F9FA;
    transition: border-color 0.2s, box-shadow 0.2s;
}
input:focus, select:focus {
    outline: none;
    border-color: var(--accent-color);
    box-shadow: 0 0 0 3px rgba(68, 138, 255, 0.25);
}
input[readonly] { background-color: #e9ecef; cursor: default; }

.file-input-wrapper { display: flex; gap: 10px; }
.file-input-wrapper input { flex-grow: 1; }
.file-input-wrapper .btn { flex-shrink: 0; }
.hidden { display: none !important; }

/* --- Main Screen State Transitions --- */
.state-card {
    display: none;
    opacity: 0;
    transform: translateY(10px);
    transition: opacity 0.3s ease, transform 0.3s ease;
}
.state-card.active { display: block; opacity: 1; transform: translateY(0); }

/* --- Info & Lists --- */
.info-box {
    background-color: #e9f5ff;
    border: 1px solid #b3d7ff;
    border-radius: var(--border-radius);
    padding: 20px;
    line-height: 1.8;
}
.info-box strong { color: var(--primary-dark); }
.form-header-info { padding: 15px 25px; background-color: #e8eaf6; text-align: center; color: var(--primary-dark); }
.data-list-container { display: flex; flex-direction: column; gap: 20px; }
.record-card .info-text { line-height: 1.7; color: var(--text-secondary-color); margin-bottom: 15px; }
.record-card .info-text b { color: var(--text-color); }

/* --- Popups --- */
#popup-overlay { position: fixed; top: 0; left: 0; width: 100%; height: 100%; background: rgba(0, 0, 0, 0.6); display: flex; justify-content: center; align-items: center; z-index: 1000; opacity: 0; visibility: hidden; transition: opacity 0.2s; }
#popup-overlay:not(.hidden) { opacity: 1; visibility: visible; }
#popup-box { background: white; border-radius: var(--border-radius); width: 90%; max-width: 500px; box-shadow: 0 10px 25px rgba(0,0,0,0.1); transform: scale(0.95); transition: transform 0.2s; }
#popup-overlay:not(.hidden) #popup-box { transform: scale(1); }
#popup-title { font-size: 1.25rem; padding: 20px; border-bottom: 1px solid var(--border-color); }
#popup-content { padding: 20px; max-height: 60vh; overflow-y: auto; }
#popup-actions { padding: 20px; display: flex; justify-content: flex-end; gap: 10px; border-top: 1px solid var(--border-color); background-color: #f8f9fa; }
.popup-form-content .form-grid { display: grid; grid-template-columns: 1fr; gap: 15px; }

/* --- Spinner --- */
.spinner { width: 40px; height: 40px; border: 4px solid #f3f3f3; border-top: 4px solid var(--primary-color); border-radius: 50%; animation: spin 1s linear infinite; margin: 10px auto; }
@keyframes spin { 0% { transform: rotate(0deg); } 100% { transform: rotate(360deg); } }

/* 配对卡片样式 */
.paired-meter-card {
    border: 1px solid var(--border-color);
    border-radius: var(--border-radius);
    margin-bottom: 25px;
    overflow: hidden; /* 保证子元素圆角 */
    background-color: #fdfdff;
}
.old-meter-info {
    padding: 15px 20px;
    background-color: #e8eaf6; /* 淡蓝色背景突出旧表信息 */
    color: var(--primary-dark);
}
.old-meter-info h3 { font-size: 1.1rem; margin: 0 0 10px 0; }
.old-meter-info .info-pair { display: flex; justify-content: space-between; }
.old-meter-info .info-pair span { font-size: 0.9rem; }
.new-meter-form { padding: 20px; }
.new-meter-form .form-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 15px 20px; }
.new-meter-form .form-group.full-width { grid-column: 1 / -1; }

/* 批次状态显示区域 */
#batch-status-container { border-top: 1px solid var(--border-color); }
#batch-status { width: 100%; text-align: left; padding: 15px; background-color: #e6f7ff; border-color: #91d5ff; }
#batch-status ul { list-style-type: none; padding-left: 0; margin-top: 10px; }
#batch-status ul li { font-size: 0.9rem; color: var(--text-secondary-color); }

/* ========================================= */
/* --- 响应式设计: 针对小屏幕设备的优化 --- */
/* ========================================= */
@media (max-width: 600px) {
    body { padding: 10px; }
    .app-container { gap: 20px; }
    .app-header h1 { font-size: 1.8rem; }

    /* 按钮组垂直堆叠，并将第一个按钮（返回按钮）置于底部 */
    .button-group, .app-nav {
        flex-direction: column-reverse; /* 关键属性 */
        gap: 10px;
    }
    .card-header, .card-content, .card-footer { padding: 15px; }
    .file-input-wrapper { flex-direction: column; }
    .new-meter-form .form-grid, .popup-form-content .form-grid { grid-template-columns: 1fr; }
    .record-card .card-content { flex-direction: column; }
    .record-card .button-group { flex-direction: row; }
    #popup-box { width: 95%; max-width: none; }
    #popup-actions { flex-direction: column-reverse; }
}