:root {
    color-scheme: light;
    --md-sys-color-primary: #1a73e8;
    --md-sys-color-on-primary: #ffffff;
    --md-sys-color-primary-container: #d3e3fd;
    --md-sys-color-on-primary-container: #041e49;
    --md-sys-color-surface: #fffbfe;
    --md-sys-color-surface-container: #f3edf7;
    --md-sys-color-surface-container-high: #ece6f0;
    --md-sys-color-on-surface: #1d1b20;
    --md-sys-color-on-surface-variant: #49454f;
    --md-sys-color-outline-variant: #cac4d0;
    --page-gradient-start: #f3edf7;
    --page-gradient-end: #e8def8;
    --brand-red: #ea4335;
    --brand-yellow: #fbbc04;
    --brand-blue: #4285f4;
    --brand-green: #34a853;
    --center-glow: rgba(255, 255, 255, 0.18);
    --control-container: var(--md-sys-color-surface-container-high);
    --control-container-hover: color-mix(in srgb, var(--md-sys-color-on-surface) 8%, var(--control-container));
    --control-container-selected: rgba(255, 255, 255, 0.78);
    --control-outline: var(--md-sys-color-outline-variant);
    --control-shadow: rgba(29, 27, 32, 0.08);
    --brand-gradient: linear-gradient(
        135deg,
        var(--brand-blue) 0%,
        var(--brand-green) 34%,
        var(--brand-yellow) 66%,
        var(--brand-red) 100%
    );
    --app-header-height: 72px;
    --app-content-padding: 32px;
    --app-content-max-width: 840px;
    font-family:
        "Noto Sans SC",
        "Noto Sans CJK SC",
        "Microsoft YaHei UI",
        "Microsoft YaHei",
        system-ui,
        sans-serif;
}

* {
    box-sizing: border-box;
}

body {
    min-width: 320px;
    height: 100vh;
    margin: 0;
    overflow: hidden;
    color: var(--md-sys-color-on-surface);
    background:
        radial-gradient(circle at 18% 18%, rgba(66, 133, 244, 0.36), transparent 34vmax),
        radial-gradient(circle at 82% 18%, rgba(251, 188, 4, 0.36), transparent 32vmax),
        radial-gradient(circle at 22% 82%, rgba(52, 168, 83, 0.3), transparent 34vmax),
        radial-gradient(circle at 82% 78%, rgba(234, 67, 53, 0.28), transparent 32vmax),
        radial-gradient(ellipse at 50% 50%, var(--center-glow), transparent 42vmax),
        linear-gradient(115deg, rgba(66, 133, 244, 0.14), rgba(52, 168, 83, 0.1) 34%, rgba(251, 188, 4, 0.12) 66%, rgba(234, 67, 53, 0.12)),
        linear-gradient(135deg, var(--page-gradient-start), var(--page-gradient-end));
}

.app-header {
    position: fixed;
    top: 0;
    right: 0;
    left: 0;
    z-index: 10;
    display: flex;
    align-items: center;
    gap: 12px;
    height: var(--app-header-height);
    padding: 0 24px;
}

.app-header__logo {
    width: 32px;
    height: 32px;
    border-radius: 10px;
}

.app-header__title {
    font-size: 1.25rem;
    font-weight: 700;
}

.visually-hidden {
    position: absolute;
    width: 1px;
    height: 1px;
    padding: 0;
    margin: -1px;
    overflow: hidden;
    white-space: nowrap;
    border: 0;
    clip: rect(0 0 0 0);
}

.language-menu {
    position: relative;
    margin-left: auto;
}

.theme-menu {
    position: relative;
}

.app-header__icon-button {
    padding: 0;
    font: inherit;
    cursor: pointer;
    background: transparent;
    border: 0;
}

.app-header__icon-button[aria-expanded="true"] {
    background: var(--control-container-selected);
}

.theme-menu .app-header__icon-link {
    margin-left: 0;
}

.language-list,
.theme-list {
    position: absolute;
    top: calc(100% + 8px);
    right: 0;
    z-index: 20;
    display: grid;
    min-width: 152px;
    padding: 8px;
    background: var(--control-container);
    border: 1px solid var(--control-outline);
    border-radius: 18px;
    box-shadow: 0 6px 16px var(--control-shadow);
}

.language-list[hidden],
.theme-list[hidden] {
    display: none;
}

.language-option,
.theme-option {
    min-height: 40px;
    padding: 0 14px;
    color: var(--md-sys-color-on-surface);
    font: inherit;
    font-size: 0.92rem;
    font-weight: 600;
    text-align: left;
    cursor: pointer;
    background: transparent;
    border: 0;
    border-radius: 9999px;
}

.language-option:hover,
.language-option:focus-visible,
.theme-option:hover,
.theme-option:focus-visible {
    background: var(--control-container-hover);
    outline: none;
}

.language-option[aria-selected="true"],
.theme-option[aria-selected="true"] {
    color: var(--md-sys-color-on-primary-container);
    background: var(--control-container-selected);
}

.app-header__icon-link {
    display: inline-grid;
    width: 48px;
    height: 48px;
    color: var(--md-sys-color-on-surface);
    text-decoration: none;
    border-radius: 9999px;
    place-items: center;
    transition: background-color 160ms ease;
}

.app-header__icon-link:hover {
    background: var(--control-container-hover);
}

.app-header__icon-link:focus-visible {
    outline: 3px solid var(--md-sys-color-primary-container);
    outline-offset: 2px;
}

.app-header__brand-icon {
    width: 24px;
    height: 24px;
    fill: currentColor;
}

.app-content {
    width: 100%;
    min-height: calc(100vh - var(--app-header-height));
    margin: var(--app-header-height) auto 0;
    padding: var(--app-content-padding);
    overflow: auto;
}

.product-panel {
    display: grid;
    grid-template-columns: auto minmax(0, 1fr);
    align-items: center;
    width: min(100%, 960px);
    gap: 28px;
    margin: 0 auto;
    padding: 48px 0;
}

.product-logo {
    width: 112px;
    height: 112px;
    border-radius: 24px;
    filter:
        drop-shadow(0 10px 18px rgba(66, 133, 244, 0.22))
        drop-shadow(0 12px 24px rgba(234, 67, 53, 0.14));
}

.product-copy {
    display: grid;
    min-width: 0;
    gap: 10px;
}

.product-title {
    margin: 0;
    color: var(--md-sys-color-on-surface);
    font-size: clamp(3.5rem, 9vw, 5.5rem);
    line-height: 0.92;
    overflow-wrap: anywhere;
}

.product-tagline {
    margin: 0;
    color: var(--md-sys-color-on-surface);
    font-size: clamp(1.05rem, 2.2vw, 1.32rem);
    line-height: 1.45;
}

.product-subtitle {
    order: -1;
    margin: 0;
    color: transparent;
    font-size: 0.88rem;
    font-weight: 700;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    background: var(--brand-gradient);
    background-clip: text;
}

.product-actions {
    display: flex;
    align-items: center;
    flex-wrap: wrap;
    gap: 14px 18px;
    margin-top: 10px;
}

.download-button {
    position: relative;
    isolation: isolate;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    min-height: 56px;
    min-width: 196px;
    padding: 0 28px;
    color: var(--md-sys-color-on-surface);
    font-size: 1rem;
    font-weight: 700;
    text-decoration: none;
    background: var(--control-container);
    border: 1px solid var(--control-outline);
    border-radius: 28px;
    box-shadow:
        0 1px 2px rgba(29, 27, 32, 0.12),
        0 1px 3px var(--control-shadow);
    transition:
        background-color 160ms ease,
        box-shadow 160ms ease,
        transform 160ms ease;
}

.download-button:hover {
    background: var(--control-container-hover);
    box-shadow:
        0 2px 4px rgba(29, 27, 32, 0.12),
        0 2px 6px var(--control-shadow);
    transform: translateY(-1px);
}

.download-button:focus-visible {
    outline: 3px solid var(--md-sys-color-primary-container);
    outline-offset: 4px;
}

.download-button.is-loading {
    color: var(--md-sys-color-on-surface-variant);
    pointer-events: none;
    background: var(--control-container-selected);
    box-shadow: none;
}

.download-note {
    flex: 1 1 260px;
    min-height: 1.4em;
    margin: 0;
    color: var(--md-sys-color-on-surface-variant);
    font-size: 0.92rem;
}

@media (prefers-color-scheme: dark) {
    :root:not([data-theme="light"]) {
        color-scheme: dark;
        --md-sys-color-primary: #a8c7fa;
        --md-sys-color-on-primary: #062e6f;
        --md-sys-color-primary-container: #0842a0;
        --md-sys-color-on-primary-container: #d3e3fd;
        --md-sys-color-surface: #141218;
        --md-sys-color-surface-container: #211f26;
        --md-sys-color-surface-container-high: #2b2930;
        --md-sys-color-on-surface: #e6e0e9;
        --md-sys-color-on-surface-variant: #cac4d0;
        --md-sys-color-outline-variant: #49454f;
        --page-gradient-start: #0f0d13;
        --page-gradient-end: #1d1b20;
        --center-glow: rgba(66, 133, 244, 0.08);
        --control-container: var(--md-sys-color-surface-container-high);
        --control-container-hover: color-mix(in srgb, var(--md-sys-color-on-surface) 10%, var(--control-container));
        --control-container-selected: rgba(0, 0, 0, 0.34);
        --control-outline: var(--md-sys-color-outline-variant);
        --control-shadow: rgba(0, 0, 0, 0.2);
    }

    :root:not([data-theme="light"]) .app-header__icon-link:hover,
    :root:not([data-theme="light"]) .app-header__icon-button[aria-expanded="true"] {
        background: var(--control-container-hover);
    }
}

:root[data-theme="dark"] {
    color-scheme: dark;
    --md-sys-color-primary: #a8c7fa;
    --md-sys-color-on-primary: #062e6f;
    --md-sys-color-primary-container: #0842a0;
    --md-sys-color-on-primary-container: #d3e3fd;
    --md-sys-color-surface: #141218;
    --md-sys-color-surface-container: #211f26;
    --md-sys-color-surface-container-high: #2b2930;
    --md-sys-color-on-surface: #e6e0e9;
    --md-sys-color-on-surface-variant: #cac4d0;
    --md-sys-color-outline-variant: #49454f;
    --page-gradient-start: #0f0d13;
    --page-gradient-end: #1d1b20;
    --center-glow: rgba(66, 133, 244, 0.08);
    --control-container: var(--md-sys-color-surface-container-high);
    --control-container-hover: color-mix(in srgb, var(--md-sys-color-on-surface) 10%, var(--control-container));
    --control-container-selected: rgba(0, 0, 0, 0.34);
    --control-outline: var(--md-sys-color-outline-variant);
    --control-shadow: rgba(0, 0, 0, 0.2);
}

:root[data-theme="dark"] .app-header__icon-link:hover,
:root[data-theme="dark"] .app-header__icon-button[aria-expanded="true"] {
    background: var(--control-container-hover);
}

@media (max-width: 560px) {
    :root {
        --app-content-padding: 24px;
    }

    .app-header {
        padding: 0 16px;
    }

    .product-panel {
        grid-template-columns: 1fr;
        justify-items: start;
        gap: 20px;
        padding: 36px 0;
    }

    .product-logo {
        width: 80px;
        height: 80px;
        border-radius: 20px;
    }

    .product-title {
        font-size: clamp(2.8rem, 16vw, 4.2rem);
    }

    .product-actions {
        width: 100%;
    }

    .download-button {
        width: 100%;
    }

    .download-note {
        flex-basis: 100%;
    }
}