:root {
    --bg-color: #FFFFFF;
    --text-primary: #1D1D1F;
    --text-secondary: #86868B;
    --btn-bg: #F5F5F7;
    --btn-bg-active: #E8E8ED;
    --accent-color: #0071E3;

    /* 动画物理参数 */
    --ease-spring: cubic-bezier(0.25, 0.8, 0.25, 1);
    --duration: 0.5s;
}



body {
    margin: 0;
    padding: 0;
    font-family: -apple-system, BlinkMacSystemFont, "SF Pro Display", "San Francisco", "Helvetica Neue", sans-serif;
    background-color: var(--bg-color);
    color: var(--text-primary);
    height: 100vh;
    display: flex;
    justify-content: center;
    align-items: center;
    /* 垂直居中 */
    overflow: hidden;
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

#survey-container {
    width: 100%;
    max-width: 390px;
    /* iPhone Pro 最佳宽度 */
    padding: 32px;
    box-sizing: border-box;
    display: flex;
    flex-direction: column;
    justify-content: center;
    /* 容器内内容居中 */
    min-height: 100vh;
    /* 确保全高以垂直居中 */
    padding-bottom: 10vh;
    /* 视觉校正: 略微向上偏移 */
}

/* 字体排版重构 */
.question-text {
    font-size: 34px;
    font-weight: 700;
    /* SF Pro 粗体 */
    line-height: 1.2;
    letter-spacing: -0.5px;
    /* 标题紧凑字间距 */
    margin-bottom: 56px;
    text-align: left;
    /* 杂志风格对齐 */
    transform-origin: center left;
    will-change: transform, opacity;
}

/* 按钮优化 */
.options-container {
    display: flex;
    flex-direction: column;
    gap: 16px;
    width: 100%;
}

.option-btn {
    appearance: none;
    border: none;
    background-color: var(--btn-bg);
    color: var(--text-primary);
    padding: 0 24px;
    height: 64px;
    /* 大尺寸触控区 */
    border-radius: 20px;
    /* 超椭圆质感 */
    font-size: 19px;
    font-weight: 600;
    text-align: left;
    /* 文本与问题对齐 */
    display: flex;
    align-items: center;
    cursor: pointer;
    transition: transform 0.2s var(--ease-spring), background-color 0.2s ease;
    width: 100%;
    -webkit-tap-highlight-color: transparent;
    position: relative;
    overflow: hidden;
}

.option-btn:active {
    transform: scale(0.96);
    background-color: var(--btn-bg-active);
}

/* 动画定义 */
.question-element-enter {
    opacity: 0;
    transform: translateY(10px);
    /* 减弱动效幅度 */
}

.question-element-active {
    opacity: 1;
    transform: translateY(0);
    transition: opacity 0.3s ease-out, transform 0.3s ease-out;
    /* 简化缓动曲线 */
}

.question-element-exit {
    opacity: 0;
    transform: translateY(-10px);
    transition: opacity 0.2s ease-in, transform 0.2s ease-in;
    /* 快速退场 */
    pointer-events: none;
}

/* 微妙的错落效果 */
.stagger-1 {
    transition-delay: 0.03s;
}

.stagger-2 {
    transition-delay: 0.06s;
}

.stagger-3 {
    transition-delay: 0.09s;
}

.completion-message {
    text-align: center;
}

.completion-title {
    font-size: 34px;
    font-weight: 800;
    letter-spacing: -1px;
    margin-bottom: 12px;
}

.completion-sub {
    font-size: 19px;
    color: var(--text-secondary);
    color: var(--text-secondary);
    font-weight: 500;
}

.survey-header {
    position: fixed;
    top: 24px;
    left: 24px;
    font-size: 13px;
    font-weight: 600;
    opacity: 0.4;
    letter-spacing: 1.5px;
    text-transform: uppercase;
    z-index: 10;
    pointer-events: none;
    transition: top 0.3s ease;
}

.nav-btn-inline {
    background: transparent;
    border: none;
    color: var(--text-primary);
    /* 使用主要文本颜色 (偏黑) */
    font-size: 24px;
    cursor: pointer;
    margin-bottom: 24px;
    padding: 0;
    display: flex;
    align-items: center;
    opacity: 0;
    transform: translateY(5px);
    /* 为了简洁减少位移 */
    animation: fadeInSlide 0.3s ease-out forwards;
    /* 简单缓出 */
    width: fit-content;
}

.nav-btn-inline:active {
    opacity: 0.6;
    transform: scale(0.98);
}

@keyframes fadeInSlide {
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

/* 视觉润色: 氛围与进度 */
.progress-bar {
    position: fixed;
    top: 0;
    left: 0;
    height: 4px;
    background: var(--accent-color);
    width: 0%;
    transition: width 0.5s ease;
    z-index: 100;
}

.background-orb {
    position: fixed;
    width: 80vh;
    height: 80vh;
    background: radial-gradient(circle, rgba(0, 113, 227, 0.12) 0%, rgba(0, 0, 0, 0) 70%);
    top: -30%;
    left: -20%;
    pointer-events: none;
    z-index: -1;
    filter: blur(60px);
    animation: breathe 12s infinite alternate ease-in-out;
}

@keyframes breathe {
    0% {
        transform: translate(0, 0) scale(1);
        opacity: 0.8;
    }

    100% {
        transform: translate(10%, 10%) scale(1.1);
        opacity: 0.4;
    }
}

/* 文本输入与操作 */
.text-input-area {
    width: 100%;
    background: rgba(0, 0, 0, 0.03);
    border: none;
    border-radius: 12px;
    padding: 16px;
    font-size: 17px;
    color: var(--text-primary);
    font-family: inherit;
    resize: none;
    min-height: 120px;
    margin-bottom: 24px;
    outline: none;
    box-sizing: border-box;
}

.text-input-area:focus {
    background: rgba(0, 0, 0, 0.05);
}

.action-btn {
    background-color: #004FB6;
    /* 应要求的深蓝色 */
    color: #FFFFFF;
    border: none;
    padding: 16px 32px;
    border-radius: 20px;
    font-size: 17px;
    font-weight: 600;
    cursor: pointer;
    width: 100%;
    transition: transform 0.2s ease, opacity 0.2s ease, background-color 0.2s ease;
}

.action-btn:active {
    transform: scale(0.96);
    opacity: 0.9;
    background-color: #003d8f;
}

/* 成功动画 */
.success-checkmark {
    width: 60px;
    height: 60px;
    margin-bottom: 24px;
    stroke: var(--accent-color);
    stroke-width: 3;
    fill: none;
    stroke-linecap: round;
    stroke-linejoin: round;
    stroke-dasharray: 100;
    stroke-dashoffset: 100;
    animation: drawCheck 1.2s cubic-bezier(0.25, 0.8, 0.25, 1) forwards;
}

@keyframes drawCheck {
    to {
        stroke-dashoffset: 0;
    }
}