:root {
    --md-sys-color-primary: #6750A4;
    --md-sys-color-on-primary: #FFFFFF;
    --md-sys-color-primary-container: #EADDFF;
    --md-sys-color-on-primary-container: #21005D;
    --md-sys-color-secondary: #625B71;
    --md-sys-color-on-secondary: #FFFFFF;
    --md-sys-color-secondary-container: #E8DEF8;
    --md-sys-color-on-secondary-container: #1D192B;
    --md-sys-color-tertiary: #7D5260;
    --md-sys-color-on-tertiary: #FFFFFF;
    --md-sys-color-tertiary-container: #FFD8E4;
    --md-sys-color-on-tertiary-container: #31111D;
    --md-sys-color-error: #B3261E;
    --md-sys-color-on-error: #FFFFFF;
    --md-sys-color-error-container: #F9DEDC;
    --md-sys-color-on-error-container: #410E0B;
    --md-sys-color-background: #FFFBFE;
    --md-sys-color-on-background: #1C1B1F;
    --md-sys-color-surface: #FFFBFE;
    --md-sys-color-on-surface: #1C1B1F;
    --md-sys-color-surface-variant: #E7E0EC;
    --md-sys-color-on-surface-variant: #49454F;
    --md-sys-color-outline: #79747E;
    --md-sys-color-shadow: #000000;
    --md-sys-color-inverse-surface: #313033;
    --md-sys-color-inverse-on-surface: #F4EFF4;
    --md-sys-color-inverse-primary: #D0BCFF;
}

/* 夜间模式颜色 */
[data-theme="dark"] {
    --md-sys-color-primary: #D0BCFF;
    --md-sys-color-on-primary: #371E73;
    --md-sys-color-primary-container: #4F378B;
    --md-sys-color-on-primary-container: #EADDFF;
    --md-sys-color-secondary: #CCC2DC;
    --md-sys-color-on-secondary: #332D41;
    --md-sys-color-secondary-container: #4A4458;
    --md-sys-color-on-secondary-container: #E8DEF8;
    --md-sys-color-tertiary: #EFB8C8;
    --md-sys-color-on-tertiary: #492532;
    --md-sys-color-tertiary-container: #633B48;
    --md-sys-color-on-tertiary-container: #FFD8E4;
    --md-sys-color-error: #F2B8B5;
    --md-sys-color-on-error: #601410;
    --md-sys-color-error-container: #8C1D18;
    --md-sys-color-on-error-container: #F9DEDC;
    --md-sys-color-background: #1A1A1A;
    --md-sys-color-on-background: #E6E0E9;
    --md-sys-color-surface: #1E1E1E;
    --md-sys-color-on-surface: #E6E0E9;
    --md-sys-color-surface-variant: #49454F;
    --md-sys-color-on-surface-variant: #CAC4D0;
    --md-sys-color-outline: #938F99;
    --md-sys-color-shadow: #000000;
    --md-sys-color-inverse-surface: #E6E0E9;
    --md-sys-color-inverse-on-surface: #322F35;
    --md-sys-color-inverse-primary: #6750A4;
}

body {
    font-family: 'Roboto', sans-serif;
    background-color: var(--md-sys-color-background);
    color: var(--md-sys-color-on-background);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    min-height: 100vh;
    margin: 0;
}

.calculator {
    max-width: 360px;
    width: 100%;
    background-color: var(--md-sys-color-surface);
    border-radius: 28px;
    box-shadow: 0 4px 8px 0 rgba(0,0,0,0.2);
    overflow: hidden;
    display: flex;
    flex-direction: column;
}

/* 夜间模式下的阴影调整 */
[data-theme="dark"] .calculator {
    box-shadow: 0 4px 8px 0 rgba(0,0,0,0.3), 0 0 0 1px rgba(255,255,255,0.08);
}

.display {
    padding: 24px;
    background-color: var(--md-sys-color-surface-variant);
    color: var(--md-sys-color-on-surface-variant);
}

.mode-selector {
    margin-bottom: 24px;
    margin-top: 16px;
    max-width: 360px;
    width: 100%;
}

.md-outlined-select {
    position: relative;
    display: block;
}

.md-outlined-select select {
    width: 100%;
    padding: 16px;
    border-radius: 4px;
    border: 1px solid var(--md-sys-color-outline);
    background-color: var(--md-sys-color-surface);
    color: var(--md-sys-color-on-surface);
    font-size: 16px;
    -webkit-appearance: none;
    -moz-appearance: none;
    appearance: none;
    cursor: pointer;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='24' height='24' viewBox='0 0 24 24'%3E%3Cpath fill='%2349454F' d='M7 10l5 5 5-5z'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-position: right 16px center;
}

.md-outlined-select span {
    position: absolute;
    top: 16px;
    left: 16px;
    font-size: 16px;
    color: var(--md-sys-color-on-surface-variant);
    background-color: var(--md-sys-color-surface);
    padding: 0 4px;
    transition: all 0.2s ease-in-out;
    pointer-events: none;
}

.md-outlined-select select:focus + span,
.md-outlined-select select:not(:placeholder-shown) + span {
    top: -8px;
    font-size: 12px;
    color: var(--md-sys-color-primary);
}

.md-outlined-select select:focus {
    outline: none;
    border-color: var(--md-sys-color-primary);
}

.question {
    font-size: 36px;
    min-height: 48px;
    text-align: right;
    margin-bottom: 16px;
}

#answer {
    width: calc(100% - 16px);
    border: none;
    border-bottom: 2px solid var(--md-sys-color-primary);
    background-color: transparent;
    font-size: 24px;
    text-align: right;
    padding: 8px;
    color: var(--md-sys-color-on-surface-variant);
}

#answer:focus {
    outline: none;
    border-bottom: 2px solid var(--md-sys-color-primary);
}

.keypad {
    padding: 24px;
    display: grid;
    gap: 16px;
}

.inputs {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 16px;
}

input[type="number"] {
    width: calc(100% - 16px);
    padding: 16px 8px;
    border-radius: 4px;
    border: 1px solid var(--md-sys-color-outline);
    background-color: var(--md-sys-color-surface);
    color: var(--md-sys-color-on-surface);
}

button {
    -webkit-tap-highlight-color: transparent; /* 移除移动端点击蓝色背景 */
    padding: 16px;
    border-radius: 12px;
    border: none;
    font-size: 16px;
    cursor: pointer;
    background-color: var(--md-sys-color-primary-container);
    color: var(--md-sys-color-on-primary-container);
    transition: background-color 0.3s;
}

button:hover {
    background-color: var(--md-sys-color-primary-container);
    opacity: 0.8;
}

.numpad {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 5px;
}

.num-btn, #clear, #backspace, #plus-minus, #dot {
    padding: 20px;
    font-size: 20px;
    background-color: var(--md-sys-color-secondary-container);
    color: var(--md-sys-color-on-secondary-container);
}

#check {
    background-color: var(--md-sys-color-primary);
    color: var(--md-sys-color-on-primary);
    grid-column: 3;
}

@media (max-width: 400px) {
    body {
        padding: 16px;
        box-sizing: border-box;
    }

    .calculator {
        border-radius: 16px;
    }

    .mode-selector {
        margin-bottom: 16px;
    }

    .theme-toggle {
        bottom: 16px;
        left: 16px;
        width: 48px;
        height: 48px;
        font-size: 20px;
    }
}

/* 悬浮按钮样式 */
.theme-toggle {
    position: fixed;
    bottom: 24px;
    left: 24px;
    width: 56px;
    height: 56px;
    border-radius: 50%;
    background-color: var(--md-sys-color-primary);
    color: var(--md-sys-color-on-primary);
    border: none;
    cursor: pointer;
    box-shadow: 0 6px 10px 0 rgba(0,0,0,0.14), 0 1px 18px 0 rgba(0,0,0,0.12), 0 3px 5px -1px rgba(0,0,0,0.20);
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 24px;
    transition: all 0.3s ease;
    z-index: 1000;
}

.theme-toggle .material-symbols-outlined {
    color: var(--md-sys-color-on-primary);
}

.theme-toggle:hover {
    box-shadow: 0 8px 14px 0 rgba(0,0,0,0.16), 0 2px 20px 0 rgba(0,0,0,0.14), 0 4px 7px -1px rgba(0,0,0,0.22);
    transform: scale(1.05);
}

.theme-toggle:active {
    transform: scale(0.95);
}

/* 夜间模式下的悬浮按钮阴影 */
[data-theme="dark"] .theme-toggle {
    box-shadow: 0 6px 10px 0 rgba(0,0,0,0.25), 0 1px 18px 0 rgba(0,0,0,0.2), 0 3px 5px -1px rgba(0,0,0,0.3), 0 0 0 1px rgba(255,255,255,0.08);
}

[data-theme="dark"] .theme-toggle:hover {
    box-shadow: 0 8px 14px 0 rgba(0,0,0,0.3), 0 2px 20px 0 rgba(0,0,0,0.25), 0 4px 7px -1px rgba(0,0,0,0.35), 0 0 0 1px rgba(255,255,255,0.12);
    transform: scale(1.05);
}

.hidden {
    display: none;
}

#settings-page {
    display: flex;
    flex-direction: column;
    gap: 16px;
    max-width: 360px;
    width: 100%;
}

/* 夜间模式下为设置页面和总结页面添加边框 */
[data-theme="dark"] #settings-page {
    border: 1px solid rgba(255,255,255,0.08);
    border-radius: 16px;
    padding: 24px;
}

[data-theme="dark"] #summary-page {
    border: 1px solid rgba(255,255,255,0.08);
    border-radius: 16px;
    padding: 24px;
}

#summary-page {
    text-align: center;
}

/* Custom Alert Modal */
.modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background-color: rgba(0, 0, 0, 0.5);
    display: flex;
    justify-content: center;
    align-items: center;
    z-index: 2000;
}

.modal-content {
    background-color: var(--md-sys-color-surface);
    padding: 32px 24px;
    border-radius: 28px;
    box-shadow: 0 4px 8px rgba(0,0,0,0.2);
    width: 80%;
    max-width: 320px;
    text-align: center;
}

.modal-content p {
    margin: 0 0 24px;
    color: var(--md-sys-color-on-surface);
    font-size: 18px;
    line-height: 1.6;
    white-space: pre-wrap;
}

.modal-content button {
    width: 100%;
    padding: 12px;
    background-color: var(--md-sys-color-primary);
    color: var(--md-sys-color-on-primary);
    border: none;
    border-radius: 12px;
    font-size: 16px;
    cursor: pointer;
}