I don't know what's the problem

hello guys, thats 1st topic! bad... have troubles simple codes... here provide code wrote today 5 min seems incorrect:


int x=255;
int led=9;

void setup() {
  // put setup code here, run once:
  pinmode(led,output);
}

void loop() {
  // put main code here, run repeatedly:
  while(x=0){
  analogwrite(led,x);
  x=x-1;
  delay(3);
    if (x=0) {
      while(x=255){
        analogwrite(led,x);
        x=x+1;
        delay(3);
}
}
}
}



this code should fade led on pin 9 255 0 , after reaching x=0 x should raise
 again 255 , forever.     
p.s. new this...
please, in comments below, describe exact problem , provide code repaired.

code: [select]


while(x=0){
...
    if (x=0) {


oops.

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