.btn {
    background: #2b3444;
    border: 1px solid #2b3444;
    color: #e5e7eb;
    font-size: 14px;
    padding: 0 12px;
    height: 35px;
    border-radius: 6px;
    cursor: pointer;
    user-select: none;
    display: inline-flex;
    align-items: center;
    transition:
        background 0.15s ease,
        border-color 0.15s ease;
    justify-content: center;
    flex-shrink: 0;
    white-space: nowrap;
}

.btn:hover {
    background: #3a475c;
    border-color: #3a475c;
}

.btn:active {
    background: #1f2937;
    border-color: #1f2937;
}

.btn:focus {
    outline: none;
    border-color: #3b82f6;
}

/* 键盘导航聚焦环 (鼠标点击不触发, 老浏览器忽略) */
.btn:focus-visible {
    outline: 2px solid #60a5fa;
    outline-offset: 2px;
}

.btn:disabled {
    opacity: 0.4;
    cursor: not-allowed;
}

.btn-blue {
    background: #2563eb;
    border-color: #2563eb;
    color: white;
}

.btn-blue:hover {
    background: #1d4ed8;
    border-color: #1d4ed8;
}

.btn-blue:active {
    background: #1e40af;
    border-color: #1e40af;
}

.btn-red {
    background: #ef4444;
    border-color: #ef4444;
    color: white;
}

.btn-red:hover {
    background: #dc2626;
    border-color: #dc2626;
}

.btn-red:active {
    background: #b91c1c;
    border-color: #b91c1c;
}

.login-box .btn {
    width: 100%;
    height: 45px;
    margin-top: 10px;
    justify-content: center;
}