請arduino前輩幫忙check一下問題在哪

自學慢慢摸索....
以下是我的程式碼,想請教LED由暗變亮是瞬間變亮
再由亮變暗時會依delay時間做變化,想請先進幫我看看哪裡出問題??
要怎麼修改才可以使LED由暗變亮時是依delay時間做變化??
const int led = 10;
int brightness=0;
int lighten=5;
int direct=0;
void setup()
{
}
void loop()
{
if(direct=0)
{
analogWrite(led,brightness);
brightness=brightness+lighten;
delay(50);
if(brightness>=250)
direct=1;
}
else
brightness=brightness-lighten;
analogWrite(led,brightness);
delay(50);
if(brightness==0)
direct=0;
}