basics of making a gas script (making cars get gas in a gas staition)

simple script that tracks the amount of gas in a car

 Public float Gas; //in liters because unity uses metric system
 float KPL; //kilometers per liter, basically consumption rate
 vector3 LastPosition; //this will just store our last position
 vector3 CurrentPosition; //transform.position
 float change; //how many kilometers we went between updates;
 
 void start(){
 
 LastPosition = transform.position;
 CurrentPosition = transform.position;
 change = 0f;
 Gas = 10f; //the f just means 10 is a float number not an int
 KPL = 10f;
 }
 
 //were going to do this in fixed update so that 
 //the change between frames isn't really small and
 //subject to having really small changes being rounded 
 //down to zero.
 FixedUpdate(){
 CurrentPosition = transform.position;
 
 change = CurrentPosition - LastPosition; //this is in meters. we multiply by 1000 to get kilometers
 change = change * 1000;
 //change now represents how much gas we've used up between frames
 
 gas = gas - change /KPL;
 
 //now we'll save our current position as our last 
 //so we can make use of it in the next update to 
 //calculate the change in distance and know how much gas 
 //was used
 
 LastPostion = CurrentPosition;
 
 if(gas <= 0)
 {
 //disable your movement script for you car, basically 
 //without gas you can't move
 }
 
 }
 
 
 /*next we'll make a second script this will be attached to another object this will be the gas station. The gas station will have attached to it a collider MARKED AS A TRIGGER we will use the function OnTriggerEnter(Collider collider) to make it so when an object enters the bounds of the collider we check the object tag to see if it's a car and if so we increase its gas variable. Gas was earlier made public so we could modify it.
 
 
 
 float HowMuchGasYouGetFromTheStation = 10;
 
 
 void OnTriggerEnter(Collider collider){
 if(collider.gameobject.tag == "car")
 {
 collider.gameobject.getcomponent<nameOfGasScript>().gas += HowMuchGasYouGetFromTheStation;
 
 
 }
 
 this script is loaded with some issues. you can keep getting gas there is no maximum and stuff but its a great solid starting point to modify off of.