Note 7 - Warrants and Registration Rights Agreements (Tables)
 12 Months Ended
Dec. 31, 2019
Notes Tables  
Schedule of Stockholders' Equity Note, Warrants or Rights [Table Text Block]
   
Shares
   
Weighted
Average
  
   
Underlying
    
Exercise
 
   
Warrants
    
Price
  
                 
Outstanding, December 31, 2017
    
15,855,017
     $
0.18
  
                 
Granted
    
5,000,000
      
0.09
  
Canceled / Expired
    
(714,286
 )    
0.53
  
Exercised
    
-
      
-
  
                 
Outstanding, December 31, 2018
    
20,140,731
      
0.15
  
                 
Granted
    
500,000
      
0.76
  
Canceled / Expired
    
(8,829,082
 )    
0.14
  
Exercised
    
-
      
-
  
                 
Outstanding, December 31, 2019
    
11,811,649
      
0.14