LD39/game/Assets/Station.cs

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

public class Station : MonoBehaviour
{
    public float maxPower;
    public Transform gauge;

    public float powerLevel;

	// Use this for initialization
	void Start ()
	{
	    powerLevel = 0;
	}
	
	// Update is called once per frame
	void Update () {
		UpdatePowerBar();
	}

    void PowerUp(float delta)
    {
        powerLevel += delta;

        if (powerLevel >= maxPower)
            Debug.Log("Station at max power!");

        UpdatePowerBar();
    }

    private void UpdatePowerBar()
    {
        var level = powerLevel / maxPower;
        gauge.localScale = new Vector3(1, level, 1);
    }

    void OnTriggerEnter(Collider other)
    {
        if (other.CompareTag("Player"))
        {
            StartCoroutine(DrainPower(other.GetComponent<Player>()));
        }
    }

    private IEnumerator DrainPower(Player player)
    {
        while (player.PowerLevel >= 1f)
        {
            powerLevel += 1;
            player.PowerLevel -= 1f;
            UpdatePowerBar();
            yield return null;
        }
    }
}