Annual report pursuant to Section 13 and 15(d)

Note 6 - Stock-based Compensation - Summary of Stock Option Activity (Details)

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Note 6 - Stock-based Compensation - Summary of Stock Option Activity (Details) - USD ($)
 12 Months Ended
Dec. 31, 2018
Dec. 31, 2017
Outstanding at beginning of year (in shares) 3,687,679  
Outstanding at beginning of year, weighted average exercise price (in dollars per share) $ 1.50  
Granted (in shares) 470,000  
Granted, weighted average exercise price (in dollars per share) $ 0.53  
Exercised (in shares) (50,000)
Exercised, weighted average exercise price (in dollars per share)  
Canceled and forfeited (in shares) (992,510)  
Canceled and Forfeited, weighted average exercise price (in dollars per share) $ 1.86  
Expired (in shares) (7,000)  
Expired (in dollars per share) $ 0.66  
Outstanding at end of year (in shares) 3,158,169 3,687,679
Outstanding at end of year, weighted average exercise price (in dollars per share) $ 1.24 $ 1.50
Outstanding at end of year, weighted average remaining contractual life (Year) 6 years 219 days  
Outstanding at end of year, aggregate intrinsic value  
Exercisable at end of year (in shares) 1,502,173  
Exercisable at end of year, weighted average exercise price (in dollars per share) $ 1.87  
Exercisable at end of year, weighted average remaining contractual life (Year) 4 years 146 days  
Exercisable at end of year, aggregate intrinsic value