| Earnings per share calculations | 
    |   | 
      | 
    Six Months Ended October 31, | 
      | 
 
    |   | 
      | 
    2018 | 
      | 
      | 
    2017 | 
      | 
 
    | Net loss | 
      | 
    $ | 
    (2,251,937 | 
    ) | 
      | 
    $ | 
    (3,502,713 | 
    ) | 
 
    | Basic weighted average number of shares outstanding | 
      | 
      | 
    1,063,602,271 | 
      | 
      | 
      | 
    949,373,602 | 
      | 
 
    | Diluted weighted average number of shares outstanding | 
      | 
      | 
    1,063,602,271 | 
      | 
      | 
      | 
    949,373,602 | 
      | 
 
    | Basic and diluted loss per share | 
      | 
    $ | 
    (0.00 | 
    ) | 
      | 
    $ | 
    (0.00 | 
    ) | 
 
 
  
    |   | 
      | 
    Three Months Ended October 31, | 
      | 
 
    |   | 
      | 
    2018 | 
      | 
      | 
    2017 | 
      | 
 
    | Net loss | 
      | 
    $ | 
    (1,036,574 | 
    ) | 
      | 
    $ | 
    (1,814,298 | 
    ) | 
 
    | Basic weighted average number of shares outstanding | 
      | 
      | 
    1,080,708,112 | 
      | 
      | 
      | 
    973,167,811 | 
      | 
 
    | Diluted weighted average number of shares outstanding | 
      | 
      | 
    1,080,708,112 | 
      | 
      | 
      | 
    973,167,811 | 
      | 
 
    | Basic and diluted loss per share | 
      | 
    $ | 
    (0.00 | 
    ) | 
      | 
    $ | 
    (0.00 | 
    ) | 
 
 
 | 
| Schedule of potentially dilutive securities | 
    |   | 
      | 
    Six Months Ended October 31, | 
      | 
 
    |   | 
      | 
    2018 | 
      | 
      | 
    2017 | 
      | 
 
    | Excluded options | 
      | 
      | 
    96,450,000 | 
      | 
      | 
      | 
    86,250,000 | 
      | 
 
    | Excluded warrants | 
      | 
      | 
    37,305,070 | 
      | 
      | 
      | 
    53,072,437 | 
      | 
 
    | Total excluded options and warrants | 
      | 
      | 
    133,755,070 | 
      | 
      | 
      | 
    139,322,437 | 
      | 
 
 
  
    |   | 
      | 
    Three Months Ended October 31, | 
      | 
 
    |   | 
      | 
    2018 | 
      | 
      | 
    2017 | 
      | 
 
    | Excluded options | 
      | 
      | 
    96,450,000 | 
      | 
      | 
      | 
    86,250,000 | 
      | 
 
    | Excluded warrants | 
      | 
      | 
    37,305,070 | 
      | 
      | 
      | 
    53,072,437 | 
      | 
 
    | Total excluded options and warrants | 
      | 
      | 
    133,755,070 | 
      | 
      | 
      | 
    139,322,437 | 
      | 
 
 
 |