/* ===========================================================
   基础样式：重置、栅格布局、字阶
   =========================================================== */

/* ---------- Base & Reset ---------- */
*, *::before, *::after {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}

html {
    scroll-behavior: smooth;
}

body {
    font-family: var(--md-sys-typescale-font-family);
    background-color: var(--md-sys-color-background);
    color: var(--md-sys-color-on-background);
    transition: background-color var(--transition-duration) var(--transition-timing), color var(--transition-duration) var(--transition-timing);
    -webkit-font-smoothing: antialiased;
    -moz-osx-font-smoothing: grayscale;
}

a {
    color: inherit;
    text-decoration: none;
}

img {
    max-width: 100%;
    height: auto;
    display: block;
}

/* ---------- Layout ---------- */
.container {
    max-width: 1152px;
    margin-left: auto;
    margin-right: auto;
    padding-left: 1.5rem;
    padding-right: 1.5rem;
}
@media (max-width: 640px) {
    .container {
        padding-left: 1rem;
        padding-right: 1rem;
    }
}

.grid-3-col {
    display: grid;
    grid-template-columns: repeat(1, 1fr);
    gap: 1.5rem;
}
@media (min-width: 768px) {
    .grid-3-col { grid-template-columns: repeat(2, 1fr); }
}
@media (min-width: 1024px) {
    .grid-3-col { grid-template-columns: repeat(3, 1fr); }
}

.grid-4-col {
    display: grid;
    grid-template-columns: repeat(1, 1fr);
    gap: 1.5rem;
}
@media (min-width: 640px) {
    .grid-4-col { grid-template-columns: repeat(2, 1fr); }
}
@media (min-width: 768px) {
    .grid-4-col { grid-template-columns: repeat(3, 1fr); }
}
@media (min-width: 1024px) {
    .grid-4-col { grid-template-columns: repeat(4, 1fr); }
}

.divider {
    border-top: 1px solid var(--md-sys-color-outline-variant);
    margin-block: 0.5rem;
}

/* ---------- Typography ---------- */
.typescale-display-large { font-size: var(--md-sys-typescale-display-large-size); font-weight: 400; line-height: 4rem; }
.typescale-display-medium {
    font-size: var(--md-sys-typescale-display-medium-size);
    font-weight: 400;
    line-height: 3.25rem;
    margin-left: 1rem;
    margin-right: 1rem;
    word-break: break-word;
}
.typescale-headline-large { font-size: var(--md-sys-typescale-headline-large-size); font-weight: 400; line-height: 2.5rem; }
.typescale-headline-medium { font-size: var(--md-sys-typescale-headline-medium-size); font-weight: 400; line-height: 2.25rem; }
.typescale-title-large { font-size: var(--md-sys-typescale-title-large-size); font-weight: 500; line-height: 1.75rem; }
.typescale-title-medium { font-size: var(--md-sys-typescale-title-medium-size); font-weight: 500; line-height: 1.5rem; }
.typescale-label-large { font-size: var(--md-sys-typescale-label-large-size); font-weight: 500; line-height: 1.25rem; }
.typescale-body-large { font-size: var(--md-sys-typescale-body-large-size); font-weight: 400; line-height: 1.5rem; }
.typescale-body-medium { font-size: var(--md-sys-typescale-body-medium-size); font-weight: 400; line-height: 1.25rem; letter-spacing: 0.017em; }