why does this file remove all my code from the main.css file

i started learning sass and when i tried to divide my code into partial files using 7-1 pattern method there is one scss file (_button.scss ) when i put the code in it it doesnt work and suddenly sass live compiler has been stopped and the main.css remove the whole code and there are images before i remove (.btn code ) and after it before i remove .btn code

after i remove the code