:root {
    --bg: #f7f8fb;
    --surface: #ffffff;
    --surface-soft: #f1f5f9;
    --text: #111827;
    --muted: #5f6b7a;
    --line: #dbe2ea;
    --primary: #2563eb;
    --focus: rgba(37, 99, 235, 0.22);
    --radius: 8px;
}

* {
    box-sizing: border-box;
}

html {
    min-width: 320px;
}

body {
    margin: 0;
    min-height: 100vh;
    background: var(--bg);
    color: var(--text);
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", sans-serif;
    font-size: 16px;
    line-height: 1.5;
}

a {
    color: inherit;
}

.skip-link {
    position: fixed;
    top: -56px;
    left: 16px;
    z-index: 20;
    padding: 10px 14px;
    border-radius: var(--radius);
    background: var(--text);
    color: #ffffff;
    text-decoration: none;
}

.skip-link:focus {
    top: 16px;
}

.app-header {
    position: sticky;
    top: 0;
    z-index: 10;
    border-bottom: 1px solid rgba(219, 226, 234, 0.9);
    background: rgba(255, 255, 255, 0.96);
    backdrop-filter: blur(14px);
}

.header-inner {
    display: grid;
    grid-template-columns: minmax(220px, 0.9fr) minmax(520px, 1.4fr);
    align-items: center;
    gap: 14px;
    width: min(1280px, calc(100% - 32px));
    min-height: 82px;
    margin: 0 auto;
    padding: 12px 0;
}

.brand {
    display: flex;
    align-items: center;
    min-width: 0;
    gap: 12px;
}

.brand-mark {
    display: grid;
    place-items: center;
    flex: 0 0 40px;
    width: 40px;
    height: 40px;
    border-radius: var(--radius);
    background: #e0f2fe;
    color: var(--primary);
}

.brand-mark svg,
.tool-tab svg {
    stroke: currentColor;
    stroke-width: 2;
    stroke-linecap: round;
    stroke-linejoin: round;
}

.brand-mark svg {
    width: 22px;
    height: 22px;
}

h1,
p {
    margin: 0;
}

h1 {
    color: var(--text);
    font-size: 21px;
    font-weight: 700;
    letter-spacing: 0;
    line-height: 1.2;
}

.brand p {
    color: var(--muted);
}

.brand p {
    margin-top: 3px;
    font-size: 13px;
}

.tool-nav {
    display: grid;
    grid-template-columns: repeat(4, minmax(0, 1fr));
    gap: 8px;
    min-width: 0;
}

.tool-tab {
    display: flex;
    align-items: center;
    justify-content: center;
    min-width: 0;
    min-height: 44px;
    gap: 7px;
    padding: 8px 10px;
    border: 1px solid var(--line);
    border-radius: var(--radius);
    background: var(--surface);
    color: #334155;
    font-size: 14px;
    font-weight: 650;
    text-align: center;
    text-decoration: none;
    transition: border-color 0.2s, background 0.2s, color 0.2s, box-shadow 0.2s;
}

.tool-tab svg {
    flex: 0 0 18px;
    width: 18px;
    height: 18px;
}

.tool-tab span {
    min-width: 0;
    overflow-wrap: anywhere;
}

.tool-tab:hover,
.tool-tab:focus-visible {
    border-color: var(--primary);
    color: var(--primary);
    outline: none;
}

.tool-tab:focus-visible {
    box-shadow: 0 0 0 4px var(--focus);
}

.tool-tab.is-current {
    border-color: var(--primary);
    background: var(--primary);
    color: #ffffff;
    box-shadow: 0 8px 18px rgba(37, 99, 235, 0.18);
}

.app-main {
    width: 100%;
    margin: 0;
    padding: 0;
    background: #ffffff;
}

iframe {
    display: block;
    width: 100%;
    height: calc(100dvh - 83px);
    min-height: 680px;
    border: 0;
    background: #ffffff;
}

@media (max-width: 1100px) {
    .header-inner {
        grid-template-columns: 1fr;
    }

    .tool-nav {
        grid-column: 1 / -1;
        grid-row: 2;
    }

    iframe {
        height: calc(100dvh - 137px);
        min-height: 640px;
    }
}

@media (max-width: 640px) {
    .header-inner {
        grid-template-columns: 1fr;
        width: min(100% - 24px, 1280px);
        min-height: 0;
        padding: 12px 0;
    }

    .tool-nav {
        grid-column: 1;
        grid-row: 2;
        grid-template-columns: repeat(2, minmax(0, 1fr));
    }

    h1 {
        font-size: 20px;
    }

    .brand p {
        font-size: 13px;
    }

    .tool-tab {
        min-height: 48px;
        font-size: 14px;
    }

    iframe {
        height: calc(100dvh - 206px);
        min-height: 620px;
    }
}

@media (prefers-reduced-motion: reduce) {
    *,
    *::before,
    *::after {
        scroll-behavior: auto !important;
        transition-duration: 0.01ms !important;
        animation-duration: 0.01ms !important;
        animation-iteration-count: 1 !important;
    }
}