AI enemy vechicle problem

I want to know about script for control a tank. I can make it look at and follow player but I have some problem. the enemy tank don’t see player it will move to straight and when it move to something such as a wall or bigstone it can’t turn away from that object so the enemy tank will fools because it can’t move to anywhere.

That’s not an easy question - avoiding obstacles is a complex task. In this case, maybe you could use the following algorithm: each Update, cast a short ray forward; if nothing is hit, move the tank; if it hits something, enter a state where the tank will rotate a fixed angle (15 degrees, for instance) then return to idle state, where it will again verify obstacles ahead - something like this:

enum State {Idle, Chase, Attack, TurnLeft, TurnRight};
var state: State = State.Idle;
var turnSpeed: float = 60; // 60 degrees per second
var length: float = 8; // "see" 8 units ahead
private var turnAngle: float = 0; 

function Update(){
  switch (state){
    case State.Chase:
      // chase the player
    case State.Idle:
      if (!Physics.Raycast(transform.position, transform.forward, length)){
        // move the tank forward if no obstacles ahead
      } else {
        // if some obstacle in range, enter turn right state:
        state = State.TurnRight;
        turnAngle = 15;
    case State.TurnRight:
      // stay in turn mode until turnAngle ends:
      var dAngle = turnSpeed * Time.deltaTime;
      transform.Rotate(0, dAngle, 0);
      turnAngle -= dAngle;
      // when turnAngle ended, return to idle state:
      if (turnAngle <= 0) state = State.Idle;

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