How to get a smaller game window(lower resolution)?

[zzzyyds1]

How can I set the game resolution to lower than 640*480? I have tried some methods to make the window size lower than 640*480, but it was detected by the system and I was unable to enter the game. What startup items should I use or how to edit autoexec.cfg that can Let the game window size of Team Fortress2 be lower than 640*480

 

[zzzyyds1]

如果你能给我一点帮助，我将非常感激