What problem does it solve? Interfaces often feel subtly off due to small compounding details like mismatched border radii, jarring animations, or misaligned icons. This Skill provides a concrete checklist of design engineering principles to diagnose and fix those polish issues in frontend code. ## Core Features & Use Cases - 19 Core Principles: Covers concentric border radius, optical alignment, shadows vs. borders, interruptible animations, tabular numbers, font smoothing, hit areas, and icon stroke weight. - Structured Review Modes: Supports quick and full review modes with severity-rated findings tables (HIGH/MEDIUM/LOW), before/after code, verification steps, and a final verdict. - Framework-Aware Fixes: Adapts recommendations to the project's existing styling system (Tailwind, plain CSS, CSS-in-JS) and motion library (motion or framer-motion), with CSS-only fallbacks. - Use Case: When a user says a settings page "feels off", run a full review to find nested cards sharing the same radius, a transition: all on buttons, and icons with mismatched stroke weights, then output actionable fixes per file and line. ## Quick Start Review my settings page component for interface polish issues using the full review mode and list every finding with before and after code.