text: 'use strict';
  
  const SAVE_MODE_MAX = 25;
  const SAVE_MODE_OFF_MAX = 32;
  const DEFAULT_TEMP = 20;
  const MIN_TEMP = 10;
  const LOW_USAGE_LIMIT = 18;
  const MEDIUM_USAGE_LIMIT = 25;
  
  class Thermostat {
    
    constructor() {
      this._temp = DEFAULT_TEMP;
      this._MINIMUM_TEMP = MIN_TEMP;
      this._maxTemp = SAVE_MODE_MAX;
      this._saveStatus = true;
    }
    
    increaseTemp() {
      if(this._temp === this._maxTemp) {
        throw new Error('Cannot exceed max. temperature!');
      }
      this._temp++;
    }
  
    decreaseTemp() {
      if(this._temp === this._MINIMUM_TEMP) {
        throw new Error('Cannot exceed min. temperature!');
      }
      this._temp--;
    }
  
    saveModeOff() {
      this._maxTemp = SAVE_MODE_OFF_MAX;
      this._saveStatus = false;
    }
  
    saveModeOn() {
      this._maxTemp = SAVE_MODE_MAX;
      this._saveStatus = true;
    }
   
    reset() {
      this.saveModeOn();
      this._temp = DEFAULT_TEMP;
    }
  
    usage() {
      if(this._temp < LOW_USAGE_LIMIT) {
        return "LOW"
      }
      else if(this._temp <= MEDIUM_USAGE_LIMIT) {
        return "MEDIUM"
      }
      return "HIGH"
    }
  }