ion () {
            const canvas = document.getElementById('canvas');
            const ctx = canvas.getContext('2d');

            // 1. 天体定义（名字、半径、4 色填充）
            const planets = [
                { name: '太阳', radius: 50, colors: ['#f2831f', '#f15d22', '#d94125', '#a41d22'] },
                { name: '水星', radius: 4, colors: ['#5a5856', '#bfbdbc', '#8c8a89', '#f4f6f8'] },
                { name: '金星', radius: 7, colors: ['#868a8d', '#d9b392', '#f3dbc3', '#414