What am I doing wrong with my millis()?

Question

Im new to Arduino and have been trying to use the millis() function for an assignment of mine. I have had a lot of trouble trying to get the millis() function to work but now it seems to be working properly as far as I can tell through the serial viewer but it wont stop my loop once it goes higher than the run time. Im trying to stop my loop after 10 seconds, but it continues going and I feel like it has something to do with my millis().

 // Pin 13 is the LED

 int led = 13;        // pin 13 on the board
 int ledOFF = 8;      //led off time delay
 int ledON = 5;            //led on time delay
 unsigned long Timer = 0;      // store time
 int runtime = 10000;      // run loop for 10s

 void setup() {
   pinMode(led, OUTPUT);

   Serial.begin(9600);
   delay(1000);
 }

 void loop() {
   Timer = millis();
   int state = 0;
   while(millis() - Timer <= runtime){
     Serial.println(Timer);
     if(state==0){
       digitalWrite(led,LOW);
       state = 1;
       delay(ledOFF);
     }
     else{
       digitalWrite(led,HIGH);
       state = 0;
       delay(ledON);
     }
    }
   }

Answer 1

as @Andre said on comment, you give variable 'Timer' a new value each loop. One of the solution is putting Timer = millis(); on the void setup instead on void loop

Answer 2

You are always re-init Timer as millis on every loop. So millis() - Timer is probably always a few milisecond and never reaches your runtime value.