/* QuickMath 基础样式与移动端适配 */
body {
    background: #f8f9fa;
    font-family: "Microsoft YaHei", Arial, sans-serif;
    overflow-x: hidden;
}
html {
    overflow-x: hidden;
}
.card {
    box-shadow: 0 2px 8px rgba(0,0,0,0.04);
}
#timer {
    font-size: 1.1rem;
    padding: 0.4em 1em;
}
.quiz-card {
    max-width: 520px;
    margin-left: auto;
    margin-right: auto;
}
.quiz-input {
    max-width: 100px;
    min-width: 60px;
    display: inline-block;
    text-align: right;
}
.quiz-stem {
    margin-left: 4px;
    margin-right: 8px;
    font-size: 1.08em;
}

/* 自定义数字键盘样式 */
#custom-keyboard {
    position: fixed;
    z-index: 9999;
    width: 220px;
    min-width: 180px;
    max-width: 240px;
    top: 50%;
    /* left 由JS动态设置 */
    transform: translateY(-50%);
    background: #fff;
    border-radius: 10px;
    box-shadow: 0 4px 24px rgba(0,0,0,0.12);
    padding: 12px 10px 8px 10px;
    display: none;
    transition: box-shadow 0.2s;
}
#custom-keyboard .keyboard-row {
    display: flex;
    justify-content: stretch;
    margin-bottom: 6px;
}
#custom-keyboard .keyboard-btn {
    flex: 1 1 0;
    min-width: 0;
    max-width: 60px;
    font-size: 1.3em;
    margin: 2px;
    padding: 0.6em 0.2em;
    border: none;
    border-radius: 6px;
    background: #f1f3f4;
    cursor: pointer;
    transition: background 0.15s;
}
#custom-keyboard .keyboard-btn:active {
    background: #e0e0e0;
}
#custom-keyboard .keyboard-btn.wide {
    flex: 2 1 0;
}