Arduino, Dim LED with button

LukePhysComp_BrightChanger.ino

/*
Brighness Changer
 Change Brightness of an LED
 
Adapted by Luke Garwood after example 5-2 from Getting Started With Arduino by Massimo Banzi and Michael Shiloh
*/


int LEDPIN = 9; //set up variable LEDPIN as the pin to which the LED connects
int BUTTONPIN = 7; //set up variable BUTTONPIN as the pin to which the button connects

int ButtonValue; // set up variable to hold value input from BUTTONPIN. 
int Old_ButtonValue; //set up variable to determine the previous value of ButtonValue

int LightOn = 0; // Used to determine whether the light is on or off, 1 being true = on, 0 being false = off
int Brightness = 0; //sets an initial brightness of 0 (none)
unsigned long startTime = 0; //determines begginning of button press


void setup() { //function that only runs once initially
  
  pinMode(LEDPIN, OUTPUT); //pinMode(pin number, either INPUT or OUTPUT)
                          //Set up LEDPIN as an output
  pinMode(BUTTONPIN, INPUT);// Set up BUTTONPIN as an Input (it recieves information from the Arduino rather than sending information/values)
}


void loop() { //function that continues to loop
  ButtonValue = digitalRead(BUTTONPIN); //digitalRead tells us if the value for this pin is HIGH or LOW
                                        //when button is pushed down digitalRead(BUTTONPIN) returns HIGH

    if((ButtonValue == HIGH) && (Old_ButtonValue == LOW)) { //a condition that asserts if ButtonValue is read as HIGH (button is pushed)
                                                            //AND was previously LOW
      LightOn = 1 - LightOn; // this alternates LightOn to be either 1 or 0 (1 being light on, 0 light off)
      startTime = millis(); // capture a time at button press
      
      delay(10); //for debouncing purposes, putting in a delay so that only one button press is registered
    }

    

    if((ButtonValue == HIGH) && (Old_ButtonValue == HIGH)){ // conditions to tell if the button is being held down
        if(LightOn == 1 && (millis() - startTime) > 20){ //if the button is held for more than 20ms
            Brightness ++; //incrementally increase brightness
            delay(35); //delay so brightness doesn't change too quickly (longer the delay, longer it takes to reach max)

              if(Brightness > 255){ //once brightness reaches 255
                   Brightness = 0; // reset the LED back to 0
               }
          }
      }
  
Old_ButtonValue = ButtonValue; //after the above code has been executed, giving Old_ButtonValue the ButtonValue to detect the moment of button press. 

    if(LightOn == 1) { //when light clicks on
         analogWrite(LEDPIN, Brightness); //turn LED on at whatever value Brightness is at
    } else {
         analogWrite(LEDPIN, 0); // or else click light off
    }

}

this code almost works, but turns off upon button release after long press.
How can you modify the code so it doesnt turn off upon button release