ml-agents/unity-environment/Assets/ML-Agents/Examples/Hallway/Scripts/HallwayAcademy.cs

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

public class HallwayAcademy : Academy {

    public float agentRunSpeed; 
    public float agentRotationSpeed;
    public Material goalScoredMaterial; // when a goal is scored the ground will use this material for a few seconds.
    public Material failMaterial; // when fail, the ground will use this material for a few seconds. 
    public float gravityMultiplier; // use ~3 to make things less floaty

    public override void InitializeAcademy()
    {
        Physics.gravity *= gravityMultiplier;
    }

    public override void AcademyReset()
    {

    }
}