* {
    box-sizing: border-box;
}

body {
    margin: 0;
    font-family: "PingFang SC", "Microsoft YaHei", sans-serif;
    background: linear-gradient(135deg, #111827, #1f2937);
    color: #111827;
}

.login-container {
    min-height: 100vh;
    display: flex;
    align-items: center;
    justify-content: center;
    padding: 24px;
}

.login-card {
    width: 380px;
    background: #ffffff;
    border-radius: 14px;
    padding: 28px 26px 24px;
    box-shadow: 0 12px 36px rgba(0, 0, 0, 0.25);
}

.login-header {
    text-align: center;
    margin-bottom: 20px;
}

.login-header .logo {
    display: inline-flex;
    align-items: center;
    gap: 10px;
    font-size: 20px;
    font-weight: 600;
    color: #111827;
}

/* ===== Tab Bar ===== */
.tab-bar {
    display: flex;
    position: relative;
    border-bottom: 2px solid #e5e7eb;
    margin-bottom: 20px;
}

.tab-item {
    flex: 1;
    text-align: center;
    padding: 10px 0;
    font-size: 14px;
    font-weight: 500;
    color: #9ca3af;
    cursor: pointer;
    transition: color 0.25s;
    user-select: none;
}

.tab-item:hover {
    color: #6b7280;
}

.tab-item.active {
    color: #2563eb;
    font-weight: 600;
}

.tab-indicator {
    position: absolute;
    bottom: -2px;
    left: 0;
    width: 33.333%;
    height: 2px;
    background: #2563eb;
    border-radius: 1px;
    transition: transform 0.3s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ===== Auth Forms ===== */
.auth-form {
    display: none;
}

.auth-form.active {
    display: block;
    animation: fadeIn 0.25s ease;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(6px); }
    to { opacity: 1; transform: translateY(0); }
}

.form-group {
    margin-bottom: 14px;
}

.form-group label {
    display: block;
    margin-bottom: 5px;
    font-size: 13px;
    color: #374151;
    font-weight: 500;
}

.optional-hint {
    color: #9ca3af;
    font-weight: 400;
    font-size: 12px;
}

.form-group input {
    width: 100%;
    padding: 9px 12px;
    border: 1px solid #d1d5db;
    border-radius: 8px;
    font-size: 14px;
    outline: none;
    transition: border-color 0.2s, box-shadow 0.2s;
}

.form-group input:focus {
    border-color: #2563eb;
    box-shadow: 0 0 0 3px rgba(37, 99, 235, 0.15);
}

.btn-submit {
    width: 100%;
    border: none;
    background: #2563eb;
    color: #fff;
    padding: 10px 12px;
    border-radius: 8px;
    font-size: 15px;
    cursor: pointer;
    transition: background 0.2s ease;
    margin-top: 4px;
}

.btn-submit:hover {
    background: #1d4ed8;
}

.btn-submit:disabled {
    background: #93c5fd;
    cursor: not-allowed;
}

.form-message {
    margin-top: 12px;
    font-size: 13px;
    text-align: center;
    min-height: 18px;
    color: #ef4444;
}

.form-message.success {
    color: #10b981;
}