💡 关灯游戏Light Switch Puzzle
在线关灯游戏：点一盏灯，它和上下左右相邻的灯都会切换亮灭，想办法把所有灯都关掉；3×3 到 7×7 五种尺寸，每局都保证有解，带提示、显示解法、重来本局、步数与最佳记录。Play the light switch puzzle online: pressing a light toggles it and its four neighbours — switch every light off. Five board sizes from 3×3 to 7×7, every puzzle solvable, with hints, a show-solution mode, restart, move counter and best scores.
点击任意一盏灯：它自己以及上、下、左、右相邻的灯都会切换（亮变灭、灭变亮）。把所有灯全部关掉就过关。键盘：方向键移动选框，回车 按下，H 提示，R 重来，N 新游戏。Click any light: it and the lights directly above, below, left and right of it flip between on and off. Turn every light off to win. Keyboard: arrows move the cursor, Enter presses, H hint, R restart, N new game.
玩法说明与常见问题How to play & FAQ
「关灯游戏」怎么玩？How do I play Light Switch Puzzle?
棋盘上有一些灯亮着。每次点击一盏灯，这盏灯和它上下左右四个邻居都会同时改变状态（亮的熄灭、灭的点亮），角上和边上的灯邻居更少。目标是让整个棋盘全部熄灭，步数越少越好。每局谜题都是从全灭状态随机按出来的，所以一定有解。Some lights on the board are on. Each press flips the pressed light and its four orthogonal neighbours (corner and edge lights have fewer neighbours). The goal is to turn the whole board off in as few moves as possible. Every puzzle is created by random presses from an all-off board, so it is always solvable.
有什么解题技巧？Any strategy tips?
常用的“追灯法”：从第二行开始，只按上一行亮灯正下方的格子，这样一行一行把灯“赶”到最后一行；最后一行剩下的图案对应第一行该按的几格，按完再追一遍即可。实在卡住可以点「提示」。The classic “chase the lights” method: from the second row down, press only the cells directly below lit lights in the row above, pushing the lights to the last row. The pattern left in the last row tells you which top-row cells to press; press them and chase again. If you get stuck, use Hint.
按两次同一格会怎样？What happens if I press the same cell twice?
会完全抵消，相当于没按，所以最优解里每格最多按一次，而且按的先后顺序不影响结果。「显示解法」会标出最少要按哪些格。The two presses cancel out, so in an optimal solution each cell is pressed at most once and the order of presses does not matter. “Show solution” marks the fewest cells you need to press.
「关灯游戏」免费吗？需要下载吗？Is Light Switch Puzzle free? Do I need to download anything?
完全免费，无需注册、下载或安装，打开网页就能玩，手机、平板和电脑都支持；游戏完全在你的浏览器本地运行，不会上传任何数据。It is completely free with no sign-up, download or install — just open the page on a phone, tablet or computer. The game runs entirely in your browser and nothing is uploaded.