scss for循环报错怎么解决

$amount : 200;
@for $i from 1 through $amount {
$theta : ($i / $amount) 120;
$delta : ($i / $amount) pi();
$x : 200px cos($delta) cos($theta) + 200; //+200 to center our sphere in our 3D world
$y : 200px cos($delta) sin($theta) + 200; //+200 to center our sphere in our 3D world
$z : 200px * sin($delta);
text:nth-child(#{$i}){
transform: translate3d($x, $y,$z);
}
}

报错信息：
Module build failed (from ./node_modules/sass-loader/dist/cjs.js):
SassError: Undefined operation: "0.005 times pi()".
on line 482 of D:\新建文件夹\wallpaper\pages\index\index.vue
$delta : ($i / $amount) * pi();