/* 全局基础样式 */
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
a { color: inherit; }

/* 通用按钮 */
.btn {
    display: inline-block;
    padding: 10px 24px;
    background: #222;
    color: #fff;
    border: none;
    cursor: pointer;
    font-size: 14px;
    letter-spacing: 1px;
    transition: background .2s;
}
.btn:hover { background: #000; }
.btn-block { display: block; width: 100%; }

/* 输入框 */
.input {
    width: 100%;
    padding: 10px 14px;
    border: 1px solid #ddd;
    font-size: 14px;
    outline: none;
    transition: border-color .2s;
}
.input:focus { border-color: #222; }

/* 卡片 */
.card {
    background: #fff;
    padding: 24px;
    box-shadow: 0 2px 8px rgba(0,0,0,.05);
}