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

body {
    font-family: 'Courier New', 'Monaco', 'Menlo', monospace;
    min-height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    background: #0a0a0a;
    color: #00ffff;
    position: relative;
    overflow: hidden;
}

/* 返回按钮 */
.back-button {
    position: fixed;
    top: 20px;
    left: 20px;
    z-index: 1000;
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 12px 20px;
    background: rgba(0, 255, 255, 0.1);
    border: 1px solid #00ffff;
    border-radius: 4px;
    color: #00ffff;
    text-decoration: none;
    font-size: 14px;
    font-weight: 500;
    cursor: pointer;
    transition: all 0.3s ease;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.back-button:hover {
    background: rgba(0, 255, 255, 0.2);
    box-shadow: 0 0 20px rgba(0, 255, 255, 0.5);
    transform: translateY(-2px);
}

/* 动态背景 */
.background {
    position: fixed;
    width: 100vw;
    height: 100vh;
    top: 0;
    left: 0;
    z-index: 0;
    background: radial-gradient(circle at 50% 50%, #1a1a1a 0%, #0a0a0a 100%);
}

.grid-overlay {
    position: absolute;
    width: 100%;
    height: 100%;
    background-image: 
        linear-gradient(rgba(0, 255, 255, 0.1) 1px, transparent 1px),
        linear-gradient(90deg, rgba(0, 255, 255, 0.1) 1px, transparent 1px);
    background-size: 50px 50px;
    animation: gridMove 20s linear infinite;
}

@keyframes gridMove {
    0% { transform: translate(0, 0); }
    100% { transform: translate(50px, 50px); }
}

.neon-lines {
    position: absolute;
    width: 100%;
    height: 100%;
}

.neon-line {
    position: absolute;
    background: linear-gradient(90deg, transparent, #00ffff, transparent);
    opacity: 0.3;
}

.neon-line.horizontal {
    width: 100%;
    height: 2px;
    top: 30%;
    animation: lineGlow 4s ease-in-out infinite;
}

.neon-line.vertical {
    width: 2px;
    height: 100%;
    left: 70%;
    animation: lineGlow 4s ease-in-out infinite 1s;
}

.neon-line.diagonal {
    width: 200px;
    height: 2px;
    top: 60%;
    left: 20%;
    transform: rotate(45deg);
    animation: lineGlow 4s ease-in-out infinite 2s;
}

@keyframes lineGlow {
    0%, 100% { opacity: 0.1; box-shadow: 0 0 5px #00ffff; }
    50% { opacity: 0.8; box-shadow: 0 0 20px #00ffff, 0 0 40px #00ffff; }
}

/* 深色卡片容器 */
.login-container {
    position: relative;
    z-index: 10;
    width: 100%;
    max-width: 400px;
    margin: 0 20px;
}

.dark-card {
    background: rgba(20, 20, 20, 0.9);
    border: 2px solid #00ffff;
    border-radius: 8px;
    padding: 40px 30px;
    box-shadow: 
        0 0 30px rgba(0, 255, 255, 0.3),
        inset 0 0 30px rgba(0, 255, 255, 0.1);
    animation: cardGlow 3s ease-in-out infinite alternate;
    backdrop-filter: blur(10px);
}

@keyframes cardGlow {
    0% { box-shadow: 0 0 30px rgba(0, 255, 255, 0.3), inset 0 0 30px rgba(0, 255, 255, 0.1); }
    100% { box-shadow: 0 0 50px rgba(0, 255, 255, 0.5), inset 0 0 50px rgba(0, 255, 255, 0.2); }
}

.card-header {
    text-align: center;
    margin-bottom: 30px;
}

.card-header h2 {
    color: #00ffff;
    font-size: 1.8rem;
    font-weight: 700;
    margin-bottom: 8px;
    text-transform: uppercase;
    letter-spacing: 2px;
    text-shadow: 0 0 10px #00ffff;
}

.subtitle {
    color: rgba(0, 255, 255, 0.7);
    font-size: 0.8rem;
    margin-bottom: 20px;
    font-weight: 300;
    letter-spacing: 3px;
}

.header-line {
    width: 60px;
    height: 2px;
    background: linear-gradient(90deg, transparent, #00ffff, transparent);
    margin: 0 auto;
    animation: lineGlow 2s ease-in-out infinite;
}

/* 表单样式 */
.form-group {
    position: relative;
    margin-bottom: 30px;
}

.form-group input {
    width: 100%;
    padding: 15px 0;
    background: transparent;
    border: none;
    border-bottom: 1px solid rgba(0, 255, 255, 0.3);
    color: #00ffff;
    font-size: 16px;
    font-family: inherit;
    outline: none;
    transition: all 0.3s ease;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.form-group input:focus {
    border-bottom-color: #00ffff;
    text-shadow: 0 0 5px #00ffff;
}

.form-group input::placeholder {
    color: transparent;
}

.form-group label {
    position: absolute;
    left: 0;
    top: 15px;
    color: rgba(0, 255, 255, 0.6);
    font-size: 14px;
    pointer-events: none;
    transition: all 0.3s ease;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.form-group input:focus + label,
.form-group input:valid + label {
    top: -5px;
    font-size: 11px;
    color: #00ffff;
    text-shadow: 0 0 5px #00ffff;
}

.neon-border {
    position: absolute;
    bottom: 0;
    left: 50%;
    width: 0;
    height: 2px;
    background: #00ffff;
    transition: all 0.3s ease;
    transform: translateX(-50%);
    box-shadow: 0 0 10px #00ffff;
}

.form-group input:focus ~ .neon-border {
    width: 100%;
}

/* 验证码组 */
.verification-group {
    display: flex;
    align-items: flex-end;
    gap: 15px;
}

.verification-group input {
    flex: 1;
}

.verify-btn, .neon-btn-small {
    padding: 12px 20px;
    background: rgba(0, 255, 255, 0.1);
    border: 1px solid #00ffff;
    border-radius: 4px;
    color: #00ffff;
    font-size: 12px;
    font-family: inherit;
    cursor: pointer;
    transition: all 0.3s ease;
    text-transform: uppercase;
    letter-spacing: 1px;
    white-space: nowrap;
}

.verify-btn:hover:not(:disabled), .neon-btn-small:hover:not(:disabled) {
    background: rgba(0, 255, 255, 0.2);
    box-shadow: 0 0 15px rgba(0, 255, 255, 0.5);
    transform: translateY(-2px);
}

.verify-btn:disabled, .neon-btn-small:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* 登录按钮 */
.login-btn, .neon-btn {
    width: 100%;
    padding: 15px;
    background: rgba(0, 255, 255, 0.1);
    border: 2px solid #00ffff;
    border-radius: 4px;
    color: #00ffff;
    font-size: 16px;
    font-family: inherit;
    font-weight: 600;
    cursor: pointer;
    position: relative;
    overflow: hidden;
    transition: all 0.3s ease;
    margin: 25px 0;
    text-transform: uppercase;
    letter-spacing: 2px;
}

.login-btn:hover, .neon-btn:hover {
    background: rgba(0, 255, 255, 0.2);
    box-shadow: 
        0 0 20px rgba(0, 255, 255, 0.5),
        inset 0 0 20px rgba(0, 255, 255, 0.1);
    transform: translateY(-2px);
}

.btn-text {
    position: relative;
    z-index: 2;
}

.btn-glow {
    position: absolute;
    top: 0;
    left: -100%;
    width: 100%;
    height: 100%;
    background: linear-gradient(90deg, transparent, rgba(0, 255, 255, 0.3), transparent);
    transition: left 0.5s ease;
}

.login-btn:hover .btn-glow, .neon-btn:hover .btn-glow {
    left: 100%;
}

/* 附加链接 */
.additional-links {
    text-align: center;
    margin-top: 25px;
}

.neon-link {
    color: rgba(0, 255, 255, 0.7);
    text-decoration: none;
    font-size: 12px;
    transition: all 0.3s ease;
    text-transform: uppercase;
    letter-spacing: 1px;
}

.neon-link:hover {
    color: #00ffff;
    text-shadow: 0 0 10px #00ffff;
}

.divider {
    color: rgba(0, 255, 255, 0.4);
    margin: 0 15px;
}

/* 隐藏和显示动画 */
.hidden {
    display: none;
}

.fade-out {
    opacity: 0;
    transform: translateY(-20px);
    transition: all 0.3s ease;
}

/* 响应式设计 */
@media (max-width: 480px) {
    .dark-card {
        padding: 30px 20px;
        margin: 0 15px;
    }
    
    .back-button {
        top: 15px;
        left: 15px;
        padding: 10px 16px;
        font-size: 12px;
    }
    
    .verification-group {
        flex-direction: column;
        gap: 15px;
    }
    
    .verify-btn, .neon-btn-small {
        width: 100%;
    }
    
    .card-header h2 {
        font-size: 1.5rem;
    }
}