campfire/Assets/Scripts/Flame.cs

#pragma warning disable CS0618

using UnityEngine;

[ExecuteAlways]
public class Flame : MonoBehaviour {

    [Range(0, 1)]
    public float Aliveness = 1;
    public ParticleSystem System;
    public float AddFuelEffect;

    private float SecretBoost = 0f;

    // Start is called before the first frame update
    void Start() {

    }

    // Update is called once per frame
    void Update() {
        if (AddFuelEffect > 0f) {
            SecretBoost += 0.2f / (SecretBoost + 0.2f) * 2f * AddFuelEffect;
            AddFuelEffect = 0f;
        }
        if (SecretBoost > 0) {
            SecretBoost -= Time.deltaTime * 3;
        }
        float TotalAliveness = Aliveness + Mathf.Max(SecretBoost, 0);

        System.startLifetime = 1.2f + 1.8f * Aliveness;
        var em = System.emission;
        em.rateOverTime = 20 + 80 * TotalAliveness;
        var vol = System.velocityOverLifetime;
        vol.radial = 0.7f * TotalAliveness;
    }
}