Unity 風船を地面のオブジェクトと衝突し衝突する際上向きの衝撃力を与えたいです

前提・実現したいこと

風船が地面から跳ね返って見えるようにして、画面の下部から離れないようにしたいです。
また地面のタグが足りるように調整したいです。
ご教示いただければ幸いです。

発生している問題・エラーメッセージ

Tag: Ground is not defined.
UnityEngine.GameObject:CompareTag(String)
PlayerControllerX:OnCollisionEnter(Collision) (at Assets/Challenge 3/Scripts/PlayerControllerX.cs:59)

該当のソースコード

using System.Collections;
using System.Collections.Generic;
using UnityEngine;

public class PlayerControllerX : MonoBehaviour
{
public float maxHeight=18.0f;
private bool isLowEnough = true;
public bool gameOver;

public float floatForce;

private float gravityModifier = 1.5f;
private Rigidbody playerRb;

public ParticleSystem explosionParticle;
public ParticleSystem fireworksParticle;

private AudioSource playerAudio;
public AudioClip moneySound;
public AudioClip explodeSound;


// Start is called before the first frame update
void Start()
{
    Physics.gravity *= gravityModifier;
    playerAudio = GetComponent<AudioSource>();
    playerRb=GetComponent<Rigidbody>();

    // Apply a small upward force at the start of the game
    playerRb.AddForce(Vector3.up * 5, ForceMode.Impulse);

}

// Update is called once per frame
void Update()
{
    //高さ制限の判定
    //
    float ht=gameObject.transform.position.y;
    //Debug.Log("Playerの高さ:"+ht);
    // While space is pressed and player is low enough, float up
    if(ht<maxHeight){
        isLowEnough=true;
        }
        else{
            isLowEnough=false;
        }
    if (Input.GetKey(KeyCode.Space) && !gameOver&&isLowEnough)
    {
        playerRb.AddForce(Vector3.up * floatForce);
        
    }
}

private void OnCollisionEnter(Collision other)
{
   

    // if player collides with bomb, explode and set gameOver to true
    if (other.gameObject.CompareTag("Bomb"))
    {
        explosionParticle.Play();
        playerAudio.PlayOneShot(explodeSound, 1.0f);
        gameOver = true;
        Debug.Log("Game Over!");
        Destroy(other.gameObject);
    } 
    else if(other.gameObject.CompareTag("Ground") && !gameOver)
    { 
        
    }
    // if player collides with money, fireworks
    else if (other.gameObject.CompareTag("Money"))
    {
        fireworksParticle.Play();
        playerAudio.PlayOneShot(moneySound, 1.0f);
        Destroy(other.gameObject);

    }

}