User wants me to rewrite the CSS with:
1. Target style: symmetric-grid
2. Effect variant: sharp-edges (4px 4px 0px solid color shadows, 0-4px border-radius, 2-3px solid borders, snappy transitions 0.15s)
3. Fresh palette different from previous (centered-stage+soft-shadows already used)
4. Keep all selectors and layout identical

Let me choose a fresh palette. Since earlier was royal (purple), let me go with a deep teal/cyan + coral/orange palette or a forest/emerald + amber. Let me do a "symmetrical grid" theme with fresh colors:
- primary: deep teal #0f766e
- primary-dark: #115e59
- accent: #f59e0b (amber)
- surface: #f0fdfa
- text: #1e293b
- rgb primary: 15,118,110
- rgb accent: 245,158,11

Shadows: hard offset 4px 4px 0px solid color. In CSS, box-shadow can't have solid color as spread without color? Actually box-shadow syntax: offset-x offset-y blur-radius spread-radius color. A hard offset shadow without blur is box-shadow: 4px 4px 0px 0px rgba(...). The "4px 4px 0px solid color" in the brief just means solid shadows (no blur). So I'll use `4px 4px 0 0 rgba(...)`.

Border-radius: 0-4px. So --radius-sm: 2px; --radius-md: 3px; --radius-lg: 4px; --radius-xl: 4px.

Borders: 2-3px solid. For cards: 2px solid var(--color-primary).

Transitions: 0.15s ease-out.

Need to keep selectors identical. Let me make sure I preserve all selectors exactly.

Let me rewrite:

```css
:root {
    --color-primary: #0f766e;
    --color-primary-dark: #115e59;
    --color-accent: #f59e0b;
    --color-surface: #f0fdfa;
    --color-text: #1e293b;
    --rgb-primary: 15,118,110;
    --rgb-accent: 245,158,11;
    --radius-sm: 2px;
    --radius-md: 3px;
    --radius-lg: 4px;
    --radius-xl: 4px;
    --shadow-sm: 3px 3px 0 0 rgba(15,118,110,.25);
    --shadow-md: 4px 4px 0 0 rgba(15,118,110,.3);
    --shadow-lg: 6px 6px 0 0 rgba(17,94,89,.35);
    --space-section: 3rem;
    --space-card: 1.25rem;
    --space-gap: 1rem;
    --transition: 0.15s cubic-bezier(0.4, 0, 0.2, 1);
    --heading-weight: 800;
    --body-line-height: 1.75;
}
```

Wait, the layout section values must differ from previous. The original already has values. I need to keep padding/margin within ±20% of input. The space variables I can't change much. I'll keep them as-is.

Now card border: 2px solid var(--color-primary). And card:hover box-shadow: 6px 6px 0 0 ... and translateY(-4px) — wait, transform is a layout property? The instructions say transform isn't listed under NEVER CHANGE. Actually it's not listed as protected, but the card:hover has transform translateY(-4px) which is a visual effect, not layout. I can keep or adjust. Keep it.

The brief says "Hard offset shadows: 4px 4px 0px solid color". I'll make sure the shadow values use offset.

Let me keep .card border: 2px solid var(--color-primary) and border-radius: var(--radius-lg).

Now, buttons: border-radius: var(--radius-md); transition: var(--transition).

Links: color var(--color-primary).

For the cta-inner: background var(--color-surface); border-radius: var(--radius-xl); padding 3rem (same). But with sharp edges I want maybe a border: 2px solid var(--color-primary); box-shadow: var(--shadow-lg). Since .cta-inner is inside .cta. Adding box-shadow is fine, doesn't change layout.

The card hover currently uses box-shadow var(--shadow-lg) and transform translateY(-4px). Keep.

I need to also change the responsive section media queries — I can't change breakpoints but I can change anything inside? The instructions say media query breakpoints (conditions only) can't change, but values inside can change as long they're not layout. The rule inside .news-grid etc. are layout values but they're already there — the instructions say allow ±20% on padding/margin; grid-template-columns can't change. Since they must be preserved, I'll keep them identical. Actually wait, the rule says grid-template-columns must remain exact. So keep as-is.

Actually the original @media rules inside have `!important` grid definitions; keep them byte-for-byte.

Let me also check: `.faq-list { grid-template-columns: 1fr !important; }` — that's in original even though .faq-list isn't defined in the base. Keep.

Also `.testimonial-list { column-count: 1 !important; }` — column-count is not in the protected list but it's a layout property, keep.

I'll output the full CSS with same selectors, just color/shadow/radius/transition changes.

Let me double-check selector list preservation:

- :root
- body
- h1, h2, h3, h4
- section, .section
- .card, [class*="card"]
- .btn, button[class*="btn"], a[class*="btn"]
- a:not([class])
- .news-grid
- .feature-list
- .hero
- .hero-content
- .testimonial-list
- .testimonial-list > *
- .partner-grid
- .faq-wrapper
- .stats-grid
- .cta-inner
- .page-main
- .card:hover, [class*="card"]:hover
- .card
- @media (max-width: 1024px) with .news-grid, .feature-list, .partner-grid, .stats-grid, .hero-inner
- @media (max-width: 640px) with :root, .news-grid, .feature-list, .faq-list, .testimonial-list, .partner-grid, .stats-grid, .cta-inner

Yes. I'll preserve them.

One thing: original `.card { border: 1px solid rgba(...); }` — I'll change to `border: 2px solid var(--color-primary)` with the sharp edges style. That's allowed.

Also original had `--shadow-sm: 0 1px 3px rgba(0,0,0,.1), 0 1px 2px rgba(0,0,0,.06);` etc. I'll replace with hard offsets.

Let me pick consistent shadow colors:
- --shadow-sm: 3px 3px 0 0 rgba(15,118,110,0.2);
- --shadow-md: 4px 4px 0 0 rgba(15,118,110,0.28);
- --shadow-lg: 6px 6px 0 0 rgba(17,94,89,0.35);

Also add a subtle bottom hard line rgba to create the "solid color" effect? The brief says `4px 4px 0px solid color`. That's just offset no blur. I'll use 4px 4px 0 0.

Now for text-shadow: The instructions say to change text-shadow; the original has no text-shadow. I can add to h1/h2/h3/h4 maybe a subtle hard shadow? But adding text-shadow to headings could be a nice touch. Since it's a visual change, allowed. But it might affect readability. I'll add a subtle text-shadow to headings: 1px 1px 0 rgba(15,118,110,0.1). That's a decorative change, layout unaffected.

Wait, the self-check says "Colors throughout the file replaced with fresh palette?" — I'll make sure all color mentions are new.

In media query at 640px, :root overrides space vars — they are not colors, keep same values (they're within tolerance). I can keep them.

Let me write the output.

I should not include the box-shadow with `0px 0px` blur but rather offset. Use:

```
--shadow-sm: 3px 3px 0 0 rgba(var(--rgb-primary), 0.2);
```

CSS variables referencing var inside rgba is valid if --rgb-primary is set to "15,118,110". Yes.

Let me craft the full output carefully, keeping comments? The original has comments. Comments are fine to keep or remove. I'll keep minimal comments matching structure but change them? The output instructions say no AI-REWRITTEN comments. I can keep original comments or strip them. I'll keep a few structural comments but not necessary. Better to preserve comments as they were to avoid any detection? Actually they said no markdown fences, no explanations, no AI-REWRITTEN comments. I'll keep the original comments as-is to be safe.

Wait, the original comments include `/* Palette: royal | Radius: moderate | Shadow: medium */` etc. I could update them to reflect new palette: `/* Palette: teal | Radius: sharp | Shadow: hard */`. That's fine, not an AI marker.

Let me produce final CSS:

```css
/* CSSVariantEngine v3.0 — app-sport-yobosports.com.cn */
/* Palette: teal-amber | Radius: sharp | Shadow: hard */
/* Spacing: balanced | Transition: snappy */
/* Section layouts: {"news":"grid-4","features":"grid-2","hero":"overlay","testimonials":"carousel","partners":"centered","faq":"with-sidebar","stats":"grid-3","cta":"card-style"} */

:root {
    --color-primary: #0f766e;
    --color-primary-dark: #115e59;
    --color-accent: #f59e0b;
    --color-surface: #f0fdfa;
    --color-text: #1e293b;
    --rgb-primary: 15,118,110;
    --rgb-accent: 245,158,11;
    --radius-sm: 2px;
    --radius-md: 3px;
    --radius-lg: 4px;
    --radius-xl: 4px;
    --shadow-sm: 3px 3px 0 0 rgba(var(--rgb-primary), .2);
    --shadow-md: 4px 4px 0 0 rgba(var(--rgb-primary), .28);
    --shadow-lg: 6px 6px 0 0 rgba(17,94,89,.35);
    --space-section: 3rem;
    --space-card: 1.25rem;
    --space-gap: 1rem;
    --transition: 0.15s cubic-bezier(0.4, 0, 0.2, 1);
    --heading-weight: 800;
    --body-line-height: 1.75;
}

/* 基础覆盖 */
body { color: var(--color-text); line-height: var(--body-line-height); }
h1, h2, h3, h4 { font-weight: var(--heading-weight); text-shadow: 1px 1px 0 rgba(var(--rgb-primary), .1); }
section, .section { padding-top: var(--space-section); padding-bottom: var(--space-section); }
.card, [class*="card"] { border-radius: var(--radius-lg); box-shadow: var(--shadow-md); padding: var(--space-card); transition: var(--transition); border: 2px solid var(--color-primary); }
.btn, button[class*="btn"], a[class*="btn"] { border-radius: var(--radius-md); transition: var(--transition); border: 2px solid var(--color-primary-dark); }
a:not([class]) { color: var(--color-primary); transition: var(--transition); }

/* ========== Section Layout Variants ========== */

/* news: grid-4 */
/* 四列紧凑网格 */
.news-grid { display: grid; grid-template-columns: repeat(4, 1fr); gap: calc(var(--space-gap) * 0.8); }

/* features: grid-2 */
.feature-list { display: grid; grid-template-columns: repeat(2, 1fr); gap: calc(var(--space-gap) * 1.5); }

/* hero: overlay */
/* 全屏背景+文字覆盖 */
.hero { position: relative; min-height: 70vh; display: flex; align-items: center; }
.hero-content { position: relative; z-index: 1; }

/* testimonials: carousel */
/* 单条轮播 */
.testimonial-list { display: flex; overflow: hidden; } 
.testimonial-list > * { flex: 0 0 100%; }

/* partners: centered */
.partner-grid { display: flex; flex-wrap: wrap; justify-content: center; gap: 2rem; }

/* faq: with-sidebar */
/* FAQ 左 + 联系信息右 */
.faq-wrapper { display: grid; grid-template-columns: 2fr 1fr; gap: 2rem; }

/* stats: grid-3 */
.stats-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: var(--space-gap); text-align: center; }

/* cta: card-style */
.cta-inner { background: var(--color-surface); border-radius: var(--radius-xl); padding: 3rem; text-align: center; border: 2px solid var(--color-primary); box-shadow: var(--shadow-lg); }

/* Page Layout: narrow-centered */
/* 窄版居中 */
.page-main { max-width: 860px; margin: 0 auto; }

/* 条件性装饰 */
.card:hover, [class*="card"]:hover { transform: translateY(-4px); box-shadow: var(--shadow-lg); }
.card { border: 2px solid var(--color-primary); }

/* Responsive */
@media (max-width: 1024px) {
    .news-grid { grid-template-columns: repeat(2, 1fr) !important; }
    .feature-list { grid-template-columns: repeat(2, 1fr) !important; }
    .partner-grid { grid-template-columns: repeat(3, 1fr) !important; }
    .stats-grid { grid-template-columns: repeat(2, 1fr) !important; }
    .hero-inner { grid-template-columns: 1fr !important; }
}
@media (max-width: 640px) {
    :root { --space-section: 2rem; --space-card: 1rem; --space-gap: 0.75rem; }
    .news-grid { grid-template-columns: 1fr !important; }
    .feature-list { grid-template-columns: 1fr !important; }
    .faq-list { grid-template-columns: 1fr !important; }
    .testimonial-list { column-count: 1 !important; }
    .partner-grid { grid-template-columns: repeat(2, 1fr) !important; }
    .stats-grid { grid-template-columns: repeat(2, 1fr) !important; }
    .cta-inner { grid-template-columns: 1fr !important; }
}
```

Wait — original `.btn, button[class*="btn"], a[class*="btn"]` didn't have border. Adding `border: 2px solid` could change layout because border-width changes box sizing if box-sizing isn't border-box. The user says NEVER change border-width. The original has no border on buttons; adding border-width 2px might change layout. However, box-sizing might be border-box globally from the site. But to be safe: the instruction says "border-color and border-style (NOT border-width)". It also says never change padding/margin but border-width isn't listed as protected? Let me check: "🔒 NEVER CHANGE: ... border-color and border-style (NOT border-width)" — so they're saying I can change color and style, but not width. Adding a border where there was none is changing border-width from 0 to 2px. That could affect layout. I should avoid adding borders to elements that had none? But the effect variant says "Strong borders (2-3px solid)". The original `.card` has `border: 1px solid rgba(...)`, so I can change that to 2px solid — that's a width change from 1px to 2px. But the instruction says "NOT border-width". Hmm. It says border-color and border-style (NOT border-width). So they don't want border-width changed. But the effect variant explicitly wants "Strong borders (2-3px solid)" and original card already has 1px. If I keep 1px, it's not strong. But the rule takes precedence. Yet border-width affects box size, but since .card has padding, a 1px difference might be within tolerance. However the "SELF-CHECK" says "width, height, padding, margin within ±20% of input" — border-width isn't included in that check. Actually checking the NEVER CHANGE list under "📐 LAYOUT": it doesn't explicitly list border-width. The border-color/style line says "(NOT border-width)" meaning when changing border-color/style, don't alter border-width. Hmm.

Let me re-read: "• border-color and border-style (NOT border-width)" — this is in the MUST CHANGE list? Wait, it's under ✅ MUST CHANGE: "border-color and border-style (NOT border-width)". So they explicitly say I must