/* itotii 在线图片加水印 - 样式
 * 设计原则：单列居中、移动优先、无构建依赖、深色模式自适应。
 */

:root {
    --color-bg: #f5f7fa;
    --color-surface: #ffffff;
    --color-text: #1f2328;
    --color-muted: #57606a;
    --color-border: #d0d7de;
    --color-accent: #1f6feb;
    --color-accent-hover: #1858bf;
    --color-focus: #0969da;
    --radius: 8px;
    --max-width: 640px;
    --shadow-sm: 0 1px 2px rgba(31, 35, 40, 0.06);
    --shadow-md: 0 4px 12px rgba(31, 35, 40, 0.08);
    --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", "Inter",
        "Helvetica Neue", Helvetica, Arial, system-ui, sans-serif;
    --font-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, monospace;
}

@media (prefers-color-scheme: dark) {
    :root {
        --color-bg: #0d1117;
        --color-surface: #161b22;
        --color-text: #e6edf3;
        --color-muted: #8b949e;
        --color-border: #30363d;
        --color-accent: #4493f8;
        --color-accent-hover: #58a6ff;
        --color-focus: #58a6ff;
        --shadow-sm: 0 1px 2px rgba(0, 0, 0, 0.3);
        --shadow-md: 0 4px 12px rgba(0, 0, 0, 0.4);
    }
}

* {
    box-sizing: border-box;
}

html {
    -webkit-text-size-adjust: 100%;
    text-size-adjust: 100%;
}

body {
    margin: 0;
    font-family: var(--font-sans);
    font-size: 16px;
    line-height: 1.6;
    color: var(--color-text);
    background: var(--color-bg);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
}

/* 可访问性：跳过导航 */
.skip-link {
    position: absolute;
    left: -9999px;
    top: 0;
    background: var(--color-accent);
    color: #fff;
    padding: 0.5em 1em;
    border-radius: 0 0 var(--radius) 0;
    z-index: 100;
}

.skip-link:focus {
    left: 0;
}

/* 全局焦点环（不仅依赖默认） */
:focus-visible {
    outline: 2px solid var(--color-focus);
    outline-offset: 2px;
    border-radius: 4px;
}

/* 屏幕阅读器专用 */
.visually-hidden {
    position: absolute !important;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    clip: rect(0, 0, 0, 0);
    white-space: nowrap;
    border: 0;
}

/* 顶栏 */
.site-header {
    background: var(--color-surface);
    border-bottom: 1px solid var(--color-border);
    box-shadow: var(--shadow-sm);
}

.site-nav {
    max-width: var(--max-width);
    margin: 0 auto;
    padding: 0.75em 1em;
    display: flex;
    align-items: center;
    justify-content: space-between;
    flex-wrap: wrap;
    gap: 0.5em;
}

.brand {
    font-weight: 700;
    font-size: 1.125rem;
    color: var(--color-accent);
    text-decoration: none;
}

.nav-links {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    gap: 1em;
    flex-wrap: wrap;
}

.nav-links a {
    color: var(--color-muted);
    text-decoration: none;
    font-size: 0.9rem;
}

.nav-links a:hover,
.nav-links a:focus-visible {
    color: var(--color-accent);
}

/* 主容器 */
.container {
    max-width: var(--max-width);
    width: 100%;
    margin: 0 auto;
    padding: 1.5em 1em 3em;
    flex: 1;
}

/* 介绍区 */
.intro h1 {
    margin: 0 0 0.5em;
    font-size: 1.6rem;
    line-height: 1.3;
}

.intro .lead {
    margin: 0 0 1.5em;
    color: var(--color-muted);
    font-size: 0.95rem;
}

kbd {
    display: inline-block;
    padding: 0.1em 0.4em;
    font-family: var(--font-mono);
    font-size: 0.85em;
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-bottom-width: 2px;
    border-radius: 4px;
    color: var(--color-text);
}

/* 步骤卡片 */
.tool {
    display: flex;
    flex-direction: column;
    gap: 1.25em;
}

.step {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    padding: 1em 1.25em;
    box-shadow: var(--shadow-sm);
}

.step h2 {
    margin: 0 0 0.75em;
    font-size: 1.05rem;
    display: flex;
    align-items: center;
    gap: 0.5em;
}

.step-num {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 1.6em;
    height: 1.6em;
    background: var(--color-accent);
    color: #fff;
    border-radius: 50%;
    font-size: 0.85rem;
    font-weight: 700;
}

.step p {
    margin: 0.4em 0;
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 0.5em;
    line-height: 1.6;
}

.step label {
    color: var(--color-text);
    font-size: 0.9rem;
    min-width: 4.5em;
    cursor: pointer;
}

/* 表单控件 */
input[type="text"],
input[type="file"] {
    width: 100%;
    padding: 0.5em 0.6em;
    font-size: 0.95rem;
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    background: var(--color-bg);
    color: var(--color-text);
    font-family: inherit;
}

input[type="text"]:focus,
input[type="file"]:focus {
    border-color: var(--color-accent);
}

input[type="color"] {
    width: 2.5em;
    height: 2em;
    padding: 0;
    border: 1px solid var(--color-border);
    border-radius: 4px;
    background: var(--color-bg);
    cursor: pointer;
}

input[type="range"] {
    flex: 1 1 200px;
    min-width: 0;
    accent-color: var(--color-accent);
    cursor: pointer;
}

input[type="checkbox"] {
    accent-color: var(--color-accent);
    cursor: pointer;
}

button {
    padding: 0.45em 1em;
    font-size: 0.9rem;
    background: var(--color-accent);
    color: #fff;
    border: 0;
    border-radius: var(--radius);
    cursor: pointer;
    font-family: inherit;
    transition: background-color 0.15s ease;
}

button:hover:not(:disabled) {
    background: var(--color-accent-hover);
}

button:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

/* 画布 */
#graph {
    margin-top: 0.5em;
    min-height: 60px;
}

#graph canvas {
    display: block;
    width: 100%;
    height: auto;
    border: 1px dashed var(--color-border);
    border-radius: var(--radius);
    cursor: pointer;
    background: repeating-conic-gradient(
        var(--color-bg) 0% 25%,
        var(--color-surface) 0% 50%
    ) 50% / 16px 16px;
}

/* About */
.about {
    margin-top: 2em;
    padding: 1em 1.25em;
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
}

.about h2 {
    font-size: 1.15rem;
    margin: 0 0 0.6em;
}

.about p {
    margin: 0 0 0.75em;
    color: var(--color-muted);
    font-size: 0.95rem;
}

.about strong {
    color: var(--color-text);
}

.features {
    list-style: none;
    margin: 0;
    padding: 0;
    display: grid;
    gap: 0.45em;
}

.features li {
    position: relative;
    padding-left: 1.4em;
    color: var(--color-muted);
    font-size: 0.9rem;
    line-height: 1.55;
}

.features li::before {
    content: "✓";
    position: absolute;
    left: 0;
    top: 0;
    color: var(--color-accent);
    font-weight: 700;
}

.features strong {
    color: var(--color-text);
    font-weight: 600;
}

/* FAQ */
.faq {
    margin-top: 2em;
}

.faq h2 {
    font-size: 1.15rem;
    margin: 0 0 0.75em;
}

.faq details {
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    padding: 0.6em 0.9em;
    margin-bottom: 0.5em;
    box-shadow: var(--shadow-sm);
}

.faq summary {
    cursor: pointer;
    font-weight: 600;
    list-style: none;
    padding: 0.2em 0;
}

.faq summary::-webkit-details-marker {
    display: none;
}

.faq summary::before {
    content: "▸";
    display: inline-block;
    margin-right: 0.5em;
    color: var(--color-accent);
    transition: transform 0.15s ease;
}

.faq details[open] summary::before {
    transform: rotate(90deg);
}

.faq p {
    margin: 0.5em 0 0;
    color: var(--color-muted);
    font-size: 0.92rem;
}

/* 友情链接 */
.friend-links {
    margin-top: 2em;
    padding: 1em 1.25em;
    background: var(--color-surface);
    border: 1px solid var(--color-border);
    border-radius: var(--radius);
    box-shadow: var(--shadow-sm);
}

.friend-links h2 {
    font-size: 1rem;
    margin: 0 0 0.75em;
    color: var(--color-muted);
    font-weight: 600;
    letter-spacing: 0.05em;
}

.friend-links-grid {
    list-style: none;
    margin: 0;
    padding: 0;
    display: flex;
    flex-wrap: wrap;
    gap: 0.5em 0.6em;
}

.friend-links-grid li {
    flex: 0 0 auto;
}

.friend-links-grid a {
    display: inline-block;
    padding: 0.4em 0.85em;
    color: var(--color-text);
    background: var(--color-bg);
    border: 1px solid var(--color-border);
    border-radius: 999px;
    text-decoration: none;
    font-size: 0.88rem;
    line-height: 1.4;
    transition: color 0.15s ease, border-color 0.15s ease, background-color 0.15s ease;
}

.friend-links-grid a:hover,
.friend-links-grid a:focus-visible {
    color: var(--color-accent);
    border-color: var(--color-accent);
    background: var(--color-surface);
}

.friend-links-tip {
    margin: 0.8em 0 0;
    font-size: 0.8rem;
    color: var(--color-muted);
}

.friend-links-tip a {
    color: var(--color-muted);
    text-decoration: underline;
    text-underline-offset: 2px;
}

.friend-links-tip a:hover,
.friend-links-tip a:focus-visible {
    color: var(--color-accent);
}

/* 页脚 */
.site-footer {
    margin-top: 2.5em;
    padding-top: 1.5em;
    border-top: 1px solid var(--color-border);
    text-align: center;
    color: var(--color-muted);
    font-size: 0.85rem;
}

.site-footer p {
    margin: 0.3em 0;
}

.site-footer a {
    color: var(--color-muted);
    text-decoration: none;
    margin: 0 0.3em;
}

.site-footer a:hover,
.site-footer a:focus-visible {
    color: var(--color-accent);
}

.copy {
    font-size: 0.8rem;
    opacity: 0.8;
}

/* 减少动画偏好 */
@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
        transition-duration: 0.01ms !important;
    }
}

/* 移动端微调 */
@media (max-width: 480px) {
    .container {
        padding: 1em 0.75em 2em;
    }
    .intro h1 {
        font-size: 1.35rem;
    }
    .step {
        padding: 0.85em 1em;
    }
}