CatController

using UnityEngine;

[RequireComponent(typeof(Rigidbody2D))]
public class CatController : MonoBehaviour {

    public float moveSpeed;
    public float runSpeed;

    Rigidbody2D rb;
    Vector2 moveVector;
    bool isRunning;

    private void Start() {
        rb = GetComponent<Rigidbody2D>();
    }

    private void Update() {
        float x = Input.GetAxisRaw("Horizontal"); // -1, 0, 1
        float y = Input.GetAxisRaw("Vertical"); // -1, 0, 1

        moveVector = new Vector2(x, y).normalized;
        isRunning = Input.GetKey(KeyCode.LeftShift);

        if (x > 0) {
            transform.localEulerAngles = new Vector3(0, 0, 0);
        } else if (x < 0) {
            transform.localEulerAngles = new Vector3(0, 180, 0);
        }
    }

    private void FixedUpdate() { // 0.02s
        if (isRunning) {
            rb.velocity = moveVector * runSpeed;
        } else {
            rb.velocity = moveVector * moveSpeed;
        }
    }
}