I Built an AI-Powered Skin Validator (And It Teaches Your AI to Fix CSS)

When you upload a skin to the MOLTamp community, something happens before you see the publish button: a validator scans your entire looking for visual effects that aren't gated behind toggle variables.

If it finds any, it doesn't block your upload. Instead, it shows you a preview of your skin running live in the browser, lists every ungated effect grouped by family, and gives you a single button: Copy AI fix prompt.

Click it, paste it into Claude, ChatGPT, Cursor, or any AI assistant, and you get back a patched with every effect properly gated. Round trip: about 60 seconds.

Here's how we built it.

The Problem

MOLTamp skins have an Effects panel — a settings page where users can toggle and adjust every visual effect a skin produces. Scanlines, glows, CRT curvature, animations, blur effects — all controllable via sliders from 0 (off) to 2 (max boost).

This only works if the skin author wires each effect to an CSS variable. If they use without gating it, the filter runs permanently. The Effects panel shows no toggle for it. The user can't turn it off.

This is a common mistake, especially when AI tools generate skins. The AI writes beautiful CSS but doesn't know about the convention. The result: skins that look great but give users zero control.

The Validator

The validator is a pure-function CSS scanner. No AST parsing, no PostCSS, no build tools — just carefully written regex passes over the raw CSS text. It detects six families of visual effects:

1. Motion — ,
2. Glow — / with large blur,
3. Frost — ,
4. Overlay — , , animated GIF backgrounds
5. Distortion — , ,
6. Color shift —

For each detection, it checks whether the CSS rule body contains a reference (directly or via ). If not, it's flagged as ungated.

It also detects "dead toggles" — variables declared in that no rule actually reads. These create toggles in the Effects panel that do nothing when flipped.

The AI Fix Prompt

This is the part I'm most proud of. Each warning generates a self-contained prompt that embeds:

• The MOLTamp skin contract (how effects work, the 0-2 range, the discovery mechanism)
• The specific CSS that was flagged (family, property, selector)
• A suggested effect ID and gating pattern
• Instructions to apply the fix

The prompt is designed so that any AI coding assistant — even one that has never heard of MOLTamp — can act on it. It teaches the AI the convention as part of the fix request.

The result: skin authors don't need to understand the Effects panel internals. They paste the prompt, get the fix, re-upload. The validator is self-healing.

Two Surfaces, One Validator

The validator runs in two places:

1. The desktop app — when you import a skin via Settings → Skins → Import, the validator scans it and shows warnings in a preview popup before committing to your library
2. The website — when you upload to moltamp.com/community/upload, the same validator runs server-side and surfaces warnings in a full preview interstitial with the skin's CSS executing live in a sandboxed iframe

Both surfaces produce identical warnings because both run the same detection code. The spec lives in , and cross-reference comments in both validator files ensure they stay in sync.

What I Learned

Building the validator taught me something about developer tools: the best errors are ones that fix themselves. A warning that says "ungated effect on line 94" is useful. A warning that says "here's the exact prompt to paste into your AI to fix it" is transformative.

If you're building developer tools, think about the 60-second feedback loop. How fast can someone go from "I see the problem" to "it's fixed"? If the answer is "paste this prompt," you've won.