| 6. STOCK OPTIONS AND WARRANTS (Tables)
 | 6 Months Ended | 
| Oct. 31, 2016 | 
|---|
| Disclosure of Compensation Related Costs, Share-based Payments [Abstract] |  | 
| Assumptions | 
    |  |  | Six Months Ended October 31, |  |  
    |  |  | 2016 |  |  | 2015 |  |  
    | Risk-free interest rate |  |  | 1.31% |  |  |  | – |  |  
    | Expected volatility |  |  | 105% |  |  |  | – |  |  
    | Expected lives (years) |  |  | 5.0 |  |  |  | – |  |  
    | Expected dividend yield |  |  | 0.00% |  |  |  | – |  |  | 
| Employee stock option activity | 
    |  |  | Options |  |  | Weighted Average Exercise
    Price |  |  | Weighted Average Grant
    Date Fair Value per Share |  |  
    | Outstanding, April 30, 2016 |  |  | 68,050,000 |  |  | $ | 0.13 |  |  | $ | 0.09 |  |  
    | Issued |  |  | 13,100,000 |  |  |  | 0.07 |  |  |  | 0.04 |  |  
    | Exercised |  |  | – |  |  |  |  |  |  |  |  |  |  
    | Total Outstanding, October 31, 2016 |  |  | 81,150,000 |  |  |  | 0.11 |  |  |  | 0.09 |  |  
    | Total Exercisable, October 31, 2016 |  |  | 65,750,000 |  |  |  | 0.13 |  |  |  | – |  |  
    | Total Vested and expected to vest as of
    October 31, 2016 |  |  | 68,650,000 |  |  | $ | 0.13 |  |  |  | – |  |  | 
| Outstanding stock options by exercise price | 
    |  |  | Exercise Price |  |  
    | Exercise Price |  | $ | 0.19 |  |  | $ | 0.11 |  |  | $ | 0.18 |  |  | $ | 0.063 |  |  | $ | 0.069 |  |  
    | Number of Options Outstanding |  |  | 25,000,000 |  |  |  | 27,200,000 |  |  |  | 250,000 |  |  |  | 15,600,000 |  |  |  | 13,100,000 |  |  
    | Weighted Average Remaining
    Contractual Life (years) of Outstanding Options |  |  | 2.92 |  |  |  | 3.17 |  |  |  | 3.47 |  |  |  | 4.17 |  |  |  | 4.50 |  |  
    | Weighted Average Exercise Price |  | $ | 0.19 |  |  | $ | 0.11 |  |  | $ | 0.18 |  |  | $ | 0.063 |  |  | $ | 0.069 |  |  
    | Number of Options Exercisable |  |  | 25,000,000 |  |  |  | 27,200,000 |  |  |  | 250,000 |  |  |  | 13,000,000 |  |  |  | 300,000 |  |  
    | Weighted Average Exercise Price of Exercisable
    Options |  | $ | 0.19 |  |  | $ | 0.11 |  |  | $ | 0.18 |  |  | $ | 0.063 |  |  | $ | 0.069 |  |  | 
| Warrant activity | 
    |  |  |  | Warrants |  |  | Weighted Average Exercise
    Price |  |  
    | Outstanding,
    April 30, 2016 |  |  |  | 84,969,908 |  |  | $ | 0.16 |  |  
    | Issued |  |  |  | – |  |  |  | – |  |  
    | Expired |  |  |  | – |  |  |  | – |  |  
    | Total Outstanding,
    October 31, 2016 |  |  |  | 84,969,908 |  |  |  | 0.16 |  |  
    | Total Exercisable,
    October 31, 2016 |  |  |  | 84,969,908 |  |  | $ | 0.16 |  |  
    |  |  |  |  |  |  |  |  |  |  |  |  | 
| Schedule of warrants outstanding by exercise prices | 
    | Range
    of Exercise Prices |  | Number
    of Warrant Shares Exercisable at 10/31/2016 |  |  | Weighted
    Average Remaining Contractual Life |  |  | Weighted
    Average Exercise Price |  |  
    | $0.075,
    $0.11, $0.12, $0.18 and $0.25 |  |  | 84,969,908 |  |  |  | 2.05 |  |  | $ | 0.16 |  |  
    |  |  |  |  |  |  |  |  |  |  |  |  |  |  
    | Five Year Term    -    $0.075 |  |  | 1,056,000 |  |  |  | 0.94 |  |  |  |  |  |  
    | Five Year Term    -    $0.12 |  |  | 35,347,508 |  |  |  | 2.66 |  |  |  |  |  |  
    | Five Year Term    -    $0.18 |  |  | 19,811,200 |  |  |  | 1.16 |  |  |  |  |  |  
    | Five Year Term    -    $0.25 |  |  | 18,755,200 |  |  |  | 1.18 |  |  |  |  |  |  
    | Five Year Term    -    $0.11 |  |  | 10,000,000 |  |  |  | 3.39 |  |  |  |  |  |  
    |  |  |  | 84,969,908 |  |  |  |  |  |  |  |  |  |  |