/**
 * 凤凰阁登录页 - 东方奢华风格
 * 设计理念：深邃黑金、凤凰祥云、现代中式轻奢
 * 版本: 2026-04-04
 */

@import url('../../fonts/fonts.css');

/* ========================================
   CSS Variables - 东方奢华配色 (默认夜晚模式)
   ======================================== */
:root {
    /* 主色调 */
    --bg-primary: #0A0A0A;
    --bg-secondary: #141414;
    --bg-card: rgba(18, 18, 18, 0.85);
    
    /* 金色系 */
    --gold-primary: #D4A96A;
    --gold-light: #E8C88A;
    --gold-dark: #B8944A;
    --gold-shimmer: #F5DFB0;
    
    /* 中国红 */
    --red-deep: #8B1C1C;
    --red-accent: #A62C2C;
    
    /* 文字 */
    --text-primary: #F5F5F0;
    --text-secondary: #9A9A9A;
    --text-muted: #5A5A5A;
    --text-gold: #D4A96A;
    
    /* 边框 */
    --border-gold: rgba(212, 169, 106, 0.25);
    --border-gold-hover: rgba(212, 169, 106, 0.5);
    --border-subtle: rgba(255, 255, 255, 0.08);
    
    /* 阴影 */
    --shadow-card: 0 25px 50px -12px rgba(0, 0, 0, 0.6);
    --shadow-gold: 0 0 40px rgba(212, 169, 106, 0.15);
    
    /* 动画 */
    --ease-out-expo: cubic-bezier(0.16, 1, 0.3, 1);
    --ease-out-back: cubic-bezier(0.34, 1.56, 0.64, 1);
    
    /* 背景渐变 */
    --bg-gradient-start: rgba(212, 169, 106, 0.08);
    --bg-gradient-mid: rgba(139, 28, 28, 0.06);
}

/* 白天模式 */
[data-theme="day"] {
    --bg-primary: #F8F6F1;
    --bg-secondary: #EDEAE3;
    --bg-card: rgba(255, 255, 255, 0.9);
    --gold-primary: #B8944A;
    --gold-light: #D4A96A;
    --gold-dark: #8B7030;
    --gold-shimmer: #C9A855;
    --text-primary: #2C2C2C;
    --text-secondary: #5A5A5A;
    --text-muted: #8A8A8A;
    --text-gold: #B8944A;
    --border-gold: rgba(184, 148, 74, 0.3);
    --border-gold-hover: rgba(184, 148, 74, 0.5);
    --border-subtle: rgba(0, 0, 0, 0.08);
    --shadow-card: 0 25px 50px -12px rgba(0, 0, 0, 0.15);
    --shadow-gold: 0 0 40px rgba(184, 148, 74, 0.1);
    --bg-gradient-start: rgba(184, 148, 74, 0.05);
    --bg-gradient-mid: rgba(139, 100, 50, 0.03);
}

/* 护眼模式 */
[data-theme="eye"] {
    --bg-primary: #F4ECD8;
    --bg-secondary: #E8DFC8;
    --bg-card: rgba(255, 250, 235, 0.92);
    --gold-primary: #9A7B4F;
    --gold-light: #B8956A;
    --gold-dark: #7A5F35;
    --gold-shimmer: #C9A878;
    --text-primary: #3D3425;
    --text-secondary: #5A4A35;
    --text-muted: #7A6A55;
    --text-gold: #9A7B4F;
    --border-gold: rgba(154, 123, 79, 0.3);
    --border-gold-hover: rgba(154, 123, 79, 0.5);
    --border-subtle: rgba(61, 52, 37, 0.1);
    --shadow-card: 0 25px 50px -12px rgba(61, 52, 37, 0.15);
    --shadow-gold: 0 0 40px rgba(154, 123, 79, 0.1);
    --bg-gradient-start: rgba(154, 123, 79, 0.06);
    --bg-gradient-mid: rgba(139, 100, 50, 0.04);
}

/* ========================================
   Base Reset & Body
   ======================================== */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html, body {
    width: 100%;
    height: 100%;
    overflow: hidden;
}

body {
    font-family: 'Noto Serif SC', 'PingFang SC', 'Microsoft YaHei', serif;
    background: var(--bg-primary);
    color: var(--text-primary);
    display: flex;
    align-items: center;
    justify-content: center;
    min-height: 100vh;
    position: relative;
    transition: background 0.5s ease, color 0.5s ease;
}

/* ========================================
   背景装饰 - 云纹暗纹
   ======================================== */
.bg-layer {
    position: fixed;
    inset: 0;
    z-index: 0;
    pointer-events: none;
    overflow: hidden;
}

/* 渐变背景 */
.bg-gradient {
    position: absolute;
    inset: 0;
    background: 
        radial-gradient(ellipse 80% 50% at 50% -20%, var(--bg-gradient-start) 0%, transparent 50%),
        radial-gradient(ellipse 60% 40% at 80% 100%, var(--bg-gradient-mid) 0%, transparent 50%),
        linear-gradient(180deg, var(--bg-primary) 0%, var(--bg-secondary) 50%, var(--bg-primary) 100%);
    transition: background 0.5s ease;
}

/* 网格纹理 */
.bg-pattern {
    position: absolute;
    inset: 0;
    opacity: 0.03;
    background-image: 
        linear-gradient(rgba(212, 169, 106, 0.3) 1px, transparent 1px),
        linear-gradient(90deg, rgba(212, 169, 106, 0.3) 1px, transparent 1px);
    background-size: 60px 60px;
}

/* 中心光晕 */
.bg-glow {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 800px;
    height: 800px;
    background: radial-gradient(circle, var(--bg-gradient-start) 0%, transparent 70%);
    pointer-events: none;
    transition: background 0.5s ease;
}

/* 凤凰轮廓装饰 */
.phoenix-silhouette {
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 600px;
    height: 600px;
    opacity: 0.025;
    background: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 400 400'%3E%3Cpath fill='%23D4A96A' d='M200 20 C220 60 280 80 320 60 C360 40 380 80 360 120 C340 160 280 180 240 200 C280 200 340 220 360 280 C380 340 340 380 280 380 C220 380 180 340 200 280 C140 280 100 240 120 180 C80 140 100 100 140 80 C120 100 100 140 120 180 C100 160 100 120 140 100 C180 80 200 40 200 20 Z M200 60 C180 80 180 120 200 140 C220 120 220 80 200 60 Z M280 240 C300 260 320 300 300 340 C280 320 260 280 280 240 Z'/%3E%3C/svg%3E") no-repeat center;
    background-size: contain;
    animation: phoenixFloat 20s ease-in-out infinite;
    transition: opacity 0.5s ease;
}

@keyframes phoenixFloat {
    0%, 100% { transform: translate(-50%, -50%) scale(1) rotate(0deg); opacity: 0.025; }
    50% { transform: translate(-50%, -52%) scale(1.02) rotate(2deg); opacity: 0.04; }
}

/* Day mode adjustments */
[data-theme="day"] .phoenix-silhouette {
    opacity: 0.04;
}

/* 浮动光点 */
.floating-particles {
    position: absolute;
    inset: 0;
}

.particle {
    position: absolute;
    width: 4px;
    height: 4px;
    background: var(--gold-primary);
    border-radius: 50%;
    opacity: 0;
    animation: particleFloat 8s ease-in-out infinite;
}

.particle:nth-child(1) { left: 10%; top: 20%; animation-delay: 0s; }
.particle:nth-child(2) { left: 85%; top: 30%; animation-delay: 1.5s; }
.particle:nth-child(3) { left: 20%; top: 70%; animation-delay: 3s; }
.particle:nth-child(4) { left: 75%; top: 80%; animation-delay: 4.5s; }
.particle:nth-child(5) { left: 50%; top: 15%; animation-delay: 6s; }

@keyframes particleFloat {
    0%, 100% { opacity: 0; transform: translateY(0) scale(0.5); }
    50% { opacity: 0.4; transform: translateY(-30px) scale(1); }
}

/* ========================================
   主容器
   ======================================== */
#container {
    position: relative;
    z-index: 10;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    width: 100%;
    max-width: 520px;
    padding: 40px;
}

/* ========================================
   顶部控制区域
   ======================================== */
.top-controls {
    position: fixed;
    top: 20px;
    right: 20px;
    z-index: 100;
    display: flex;
    align-items: center;
    gap: 12px;
}

/* 主题切换器 */
.theme-switcher {
    display: flex;
    background: var(--bg-card);
    border: 1px solid var(--border-gold);
    border-radius: 8px;
    padding: 4px;
    gap: 2px;
    backdrop-filter: blur(10px);
    transition: background 0.5s ease, border-color 0.5s ease;
}

.theme-btn {
    width: 36px;
    height: 32px;
    border: none;
    border-radius: 6px;
    background: transparent;
    color: var(--text-muted);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.3s ease;
}

.theme-btn:hover {
    color: var(--gold-primary);
    background: rgba(212, 169, 106, 0.08);
}

.theme-btn.active {
    color: var(--gold-primary);
    background: rgba(212, 169, 106, 0.12);
}

/* 语言切换按钮 */
.lang-btn {
    padding: 8px 16px;
    background: var(--bg-card);
    border: 1px solid var(--border-gold);
    border-radius: 8px;
    color: var(--text-secondary);
    font-family: 'Noto Serif SC', 'DM Mono', sans-serif;
    font-size: 14px;
    font-weight: 500;
    letter-spacing: 0.5px;
    cursor: pointer;
    transition: all 0.3s ease, background 0.5s ease, border-color 0.5s ease;
    backdrop-filter: blur(10px);
    display: flex;
    align-items: center;
    gap: 8px;
}

.lang-btn:hover {
    background: rgba(212, 169, 106, 0.08);
    border-color: var(--gold-primary);
    color: var(--gold-primary);
}

.lang-flag {
    font-size: 18px;
    line-height: 1;
}

.lang-text {
    font-weight: 600;
}

.lang-btn:hover {
    background: rgba(212, 169, 106, 0.08);
    border-color: var(--gold-primary);
    color: var(--gold-primary);
}

.flag {
    font-size: 16px;
    line-height: 1;
}

/* ========================================
   登录卡片 - 玻璃态
   ======================================== */
#loginCard {
    width: 100%;
    background: var(--bg-card);
    border: 1px solid var(--border-gold);
    border-radius: 20px;
    padding: 50px 45px;
    box-shadow: 
        var(--shadow-card),
        var(--shadow-gold),
        inset 0 1px 0 rgba(255, 255, 255, 0.05);
    backdrop-filter: blur(20px);
    animation: cardEntrance 1s var(--ease-out-expo) forwards;
    opacity: 0;
    transform: translateY(30px);
    transition: background 0.5s ease, border-color 0.5s ease, box-shadow 0.5s ease;
}

@keyframes cardEntrance {
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* 卡片顶部装饰线 */
#loginCard::before {
    content: '';
    position: absolute;
    top: 0;
    left: 50%;
    transform: translateX(-50%);
    width: 100px;
    height: 3px;
    background: linear-gradient(90deg, transparent, var(--gold-primary), transparent);
    border-radius: 0 0 3px 3px;
}

/* ========================================
   Logo 区域 - 文字版
   ======================================== */
.logo-container {
    text-align: center;
    margin-bottom: 40px;
    animation: logoEntrance 1s var(--ease-out-expo) 0.2s forwards;
    opacity: 0;
    transform: translateY(20px);
}

@keyframes logoEntrance {
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.logo-text-main {
    font-family: 'Noto Serif SC', 'STKaiti', 'KaiTi', serif;
    font-size: 54px;
    font-weight: 700;
    color: var(--gold-primary);
    letter-spacing: 14px;
    text-shadow: 0 2px 30px rgba(212, 169, 106, 0.4);
    margin-bottom: 10px;
}

.logo-text-en {
    font-family: 'Playfair Display', 'Georgia', serif;
    font-size: 24px;
    font-weight: 600;
    font-style: italic;
    color: var(--text-secondary);
    letter-spacing: 10px;
    text-transform: uppercase;
}

/* ========================================
   隐藏原有元素
   ======================================== */
#applelogin_png,
#login_png {
    display: none !important;
}

/* ========================================
   登录表单
   ======================================== */
#login {
    animation: formEntrance 1s var(--ease-out-expo) 0.4s forwards;
    opacity: 0;
    transform: translateY(20px);
}

@keyframes formEntrance {
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

#login-error {
    background: rgba(139, 28, 28, 0.15);
    border: 1px solid rgba(166, 44, 44, 0.4);
    border-radius: 8px;
    padding: 12px 16px;
    margin-bottom: 20px;
    color: #E88;
    font-size: 14px;
    text-align: center;
    opacity: 0;
    transform: translateY(-10px);
    transition: all 0.3s ease;
}

#login-error.visible {
    opacity: 1;
    transform: translateY(0);
}

/* ========================================
   输入框
   ======================================== */
.login-field {
    position: relative;
    margin-bottom: 20px;
}

.login-field input {
    width: 100%;
    padding: 18px 20px;
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid var(--border-subtle);
    border-radius: 12px;
    color: var(--text-primary);
    font-family: 'Noto Serif SC', 'PingFang SC', sans-serif;
    font-size: 16px;
    font-weight: 500;
    letter-spacing: 1px;
    transition: all 0.4s ease;
    outline: none;
}

.login-field input::placeholder {
    color: var(--text-muted);
    font-weight: 300;
}

.login-field input:hover {
    border-color: rgba(212, 169, 106, 0.3);
    background: rgba(255, 255, 255, 0.05);
}

.login-field input:focus {
    border-color: var(--gold-primary);
    background: rgba(212, 169, 106, 0.05);
    box-shadow: 
        0 0 0 3px rgba(212, 169, 106, 0.1),
        0 0 30px rgba(212, 169, 106, 0.1);
}

/* 输入框图标 */
.login-field::before {
    position: absolute;
    left: 18px;
    top: 50%;
    transform: translateY(-50%);
    color: var(--text-muted);
    font-size: 16px;
    transition: color 0.3s ease;
    pointer-events: none;
    z-index: 1;
}

.login-field:focus-within::before {
    color: var(--gold-primary);
}

/* ========================================
   按钮
   ======================================== */
.btn-group {
    display: flex;
    gap: 15px;
    margin-top: 30px;
}

.k2-button {
    flex: 1;
    padding: 18px 30px;
    border: none;
    border-radius: 12px;
    font-family: 'Noto Serif SC', 'PingFang SC', sans-serif;
    font-size: 16px;
    font-weight: 500;
    letter-spacing: 3px;
    cursor: pointer;
    transition: all 0.4s var(--ease-out-expo);
    position: relative;
    overflow: hidden;
}

.k2-button::before {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(135deg, rgba(255,255,255,0.1) 0%, transparent 50%);
    opacity: 0;
    transition: opacity 0.3s ease;
}

.k2-button:hover::before {
    opacity: 1;
}

/* 主按钮 - 金色 */
.k2-button-style-a-green {
    background: linear-gradient(135deg, var(--gold-dark) 0%, var(--gold-primary) 50%, var(--gold-dark) 100%);
    background-size: 200% 200%;
    color: #0A0A0A;
    font-weight: 600;
    box-shadow: 
        0 4px 15px rgba(212, 169, 106, 0.3),
        inset 0 1px 0 rgba(255, 255, 255, 0.2);
    animation: buttonShine 3s ease-in-out infinite;
}

@keyframes buttonShine {
    0%, 100% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
}

.k2-button-style-a-green:hover {
    transform: translateY(-3px);
    box-shadow: 
        0 8px 25px rgba(212, 169, 106, 0.4),
        inset 0 1px 0 rgba(255, 255, 255, 0.3);
}

.k2-button-style-a-green:active {
    transform: translateY(-1px);
}

/* 次按钮 - 透明 */
.k2-button-style-a {
    background: transparent;
    border: 1px solid var(--border-gold);
    color: var(--text-secondary);
}

.k2-button-style-a:hover {
    background: rgba(212, 169, 106, 0.08);
    border-color: var(--gold-primary);
    color: var(--gold-primary);
    transform: translateY(-3px);
}

/* 按钮加载状态 */
.k2-button.is-loading {
    pointer-events: none;
    opacity: 0.7;
}

.k2-button.is-loading::after {
    content: '';
    position: absolute;
    width: 20px;
    height: 20px;
    top: 50%;
    left: 50%;
    margin: -10px 0 0 -10px;
    border: 2px solid transparent;
    border-top-color: currentColor;
    border-radius: 50%;
    animation: buttonSpinner 0.8s linear infinite;
}

@keyframes buttonSpinner {
    to { transform: rotate(360deg); }
}

/* ========================================
   虚拟键盘 - 右下角固定
   ======================================== */
#keypad {
    position: fixed;
    right: 30px;
    bottom: 80px;
    z-index: 100;
    animation: keypadEntrance 0.6s var(--ease-out-expo) 0.6s forwards;
    opacity: 0;
    transform: translateY(20px);
}

@keyframes keypadEntrance {
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.hidden-keypad {
    display: none;
}

#keypad table {
    border-collapse: separate;
    border-spacing: 6px;
    background: var(--bg-card);
    padding: 15px;
    border-radius: 16px;
    border: 1px solid var(--border-gold);
    backdrop-filter: blur(20px);
    box-shadow: var(--shadow-card);
}

.keypadbut {
    width: 60px;
    height: 50px;
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid var(--border-subtle);
    border-radius: 10px;
    color: var(--text-secondary);
    font-family: 'DM Mono', monospace;
    font-size: 18px;
    cursor: pointer;
    transition: all 0.3s ease;
}

.keypadbut:hover {
    background: rgba(212, 169, 106, 0.1);
    border-color: var(--gold-primary);
    color: var(--gold-primary);
    transform: scale(1.05);
}

.keypadbut:active {
    transform: scale(0.95);
    background: rgba(212, 169, 106, 0.15);
}

/* ========================================
   隐藏标签
   ======================================== */
.hidden-label {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    border: 0;
}

/* ========================================
   响应式设计
   ======================================== */
@media (max-width: 768px) {
    #container {
        padding: 30px 20px;
    }
    
    #loginCard {
        padding: 40px 30px;
        border-radius: 16px;
    }
    
    .logo-text-main {
        font-size: 42px;
        font-weight: 700;
        letter-spacing: 12px;
    }
    
    .logo-text-en {
        font-size: 18px;
        font-weight: 600;
        letter-spacing: 6px;
    }
    
    .k2-button {
        padding: 16px 20px;
        font-size: 15px;
        font-weight: 600;
    }
    
    .btn-group {
        flex-direction: column;
    }
    
    .keypadbut {
        width: 55px;
        height: 48px;
        font-size: 16px;
    }
    
    #keypad {
        right: 15px;
        bottom: 70px;
    }
    
    #keypad table {
        padding: 10px;
    }
}

@media (max-width: 480px) {
    #loginCard {
        padding: 35px 25px;
    }
    
    .logo-container {
        margin-bottom: 30px;
    }
    
    .logo-text-main {
        font-size: 36px;
        font-weight: 700;
        letter-spacing: 10px;
    }
    
    .logo-text-en {
        font-size: 16px;
        font-weight: 600;
        letter-spacing: 5px;
    }
    
    .login-field input {
        padding: 16px 18px;
        font-size: 15px;
        font-weight: 500;
    }
    
    .keypadbut {
        width: 48px;
        height: 44px;
        font-size: 15px;
        font-weight: 500;
    }
    
    #keypad table {
        padding: 8px;
        border-spacing: 5px;
    }
    
    #keypad {
        right: 10px;
        bottom: 60px;
    }
    
    .top-controls {
        top: 12px;
        right: 12px;
        gap: 8px;
    }
    
    .theme-btn {
        width: 32px;
        height: 28px;
    }
    
    .lang-btn {
        padding: 6px 12px;
        font-size: 13px;
        font-weight: 500;
    }
    
    .lang-flag {
        font-size: 16px;
    }
}

/* ========================================
   隐藏原有元素
   ======================================== */
#bgimg,
#applebut {
    display: none !important;
}

/* ========================================
   特殊效果 - 浮动文字
   ======================================== */
.float-text {
    position: fixed;
    font-family: 'Playfair Display', serif;
    font-size: 120px;
    font-weight: 700;
    color: rgba(212, 169, 106, 0.015);
    pointer-events: none;
    z-index: 1;
    white-space: nowrap;
    user-select: none;
}

.float-text-left {
    left: -50px;
    top: 50%;
    transform: translateY(-50%) rotate(-90deg);
}

.float-text-right {
    right: -50px;
    top: 50%;
    transform: translateY(-50%) rotate(90deg);
}

/* ========================================
   安全加固 & 覆盖旧样式
   ======================================== */
#form1 {
    float: none !important;
}

/* 覆盖 loading.v3.css 的容器样式 */
#container {
    position: relative !important;
    z-index: 10 !important;
    display: flex !important;
    flex-direction: column !important;
    align-items: center !important;
    justify-content: center !important;
    width: 100% !important;
    max-width: 520px !important;
    padding: 40px !important;
    margin: 0 auto !important;
    overflow: visible !important;
}

#container .t1 {
    display: block !important;
    width: 100% !important;
    max-width: 100% !important;
    margin: 0 !important;
    padding: 0 !important;
    background: transparent !important;
    box-shadow: none !important;
    border: none !important;
    border-radius: 0 !important;
    line-height: normal !important;
    text-align: left !important;
    font-family: inherit !important;
    font-size: inherit !important;
}

/* 隐藏旧版元素 */
#bgimg {
    display: none !important;
}

/* 按钮组覆盖 */
#login .btn-group {
    display: flex;
    gap: 15px;
    margin-top: 30px;
}

#login .k2-button {
    flex: 1;
    padding: 18px 30px;
    border: none;
    border-radius: 12px;
    font-family: 'Noto Serif SC', 'PingFang SC', sans-serif;
    font-size: 16px;
    font-weight: 500;
    letter-spacing: 3px;
    cursor: pointer;
    transition: all 0.4s var(--ease-out-expo);
    position: relative;
    overflow: hidden;
}

#login .k2-button::before {
    content: '';
    position: absolute;
    inset: 0;
    background: linear-gradient(135deg, rgba(255,255,255,0.1) 0%, transparent 50%);
    opacity: 0;
    transition: opacity 0.3s ease;
}

#login .k2-button:hover::before {
    opacity: 1;
}

#login .k2-button-style-a-green {
    background: linear-gradient(135deg, var(--gold-dark) 0%, var(--gold-primary) 50%, var(--gold-dark) 100%);
    background-size: 200% 200%;
    color: #0A0A0A;
    font-weight: 600;
    box-shadow: 
        0 4px 15px rgba(212, 169, 106, 0.3),
        inset 0 1px 0 rgba(255, 255, 255, 0.2);
    animation: buttonShine 3s ease-in-out infinite;
}

@keyframes buttonShine {
    0%, 100% { background-position: 0% 50%; }
    50% { background-position: 100% 50%; }
}

#login .k2-button-style-a-green:hover {
    transform: translateY(-3px);
    box-shadow: 
        0 8px 25px rgba(212, 169, 106, 0.4),
        inset 0 1px 0 rgba(255, 255, 255, 0.3);
}

#login .k2-button-style-a-green:active {
    transform: translateY(-1px);
}

#login .k2-button-style-a {
    background: transparent;
    border: 1px solid var(--border-gold);
    color: var(--text-secondary);
}

#login .k2-button-style-a:hover {
    background: rgba(212, 169, 106, 0.08);
    border-color: var(--gold-primary);
    color: var(--gold-primary);
    transform: translateY(-3px);
}

#login .k2-button.is-loading {
    pointer-events: none;
    opacity: 0.7;
}

#login .k2-button.is-loading::after {
    content: '';
    position: absolute;
    width: 20px;
    height: 20px;
    top: 50%;
    left: 50%;
    margin: -10px 0 0 -10px;
    border: 2px solid transparent;
    border-top-color: currentColor;
    border-radius: 50%;
    animation: buttonSpinner 0.8s linear infinite;
}

@keyframes buttonSpinner {
    to { transform: rotate(360deg); }
}

/* 移动端按钮 */
@media (max-width: 768px) {
    #login .btn-group {
        flex-direction: column;
    }
}