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Note 5 - Stockholders' Equity (Deficit) (Tables)
12 Months Ended
Dec. 31, 2021
Notes Tables  
Share-based Payment Arrangement, Option, Activity [Table Text Block]
  

Number of shares

  

Weighted average exercise price

  Weighted average remaining contractual life (years)  

Aggregate Intrinsic value

 

Outstanding as of December 31, 2019

  2,253,206  $2.60   8.19     

Granted

             

Exercised

  (85,939)  1.28        

Forfeited or expired

  (1,514,627)  3.38        

Outstanding as of December 31, 2020

  652,640  $0.91   6.38     

Granted

             

Exercised

  (148,872)  1.20        

Forfeited or expired

             

Outstanding as of December 31, 2021

  503,768  $0.83   5.33  $1,954,882 

Vested and expected to vest at December 31, 2021

  503,768  $0.83   5.33  $1,954,882 

Exercisable as of December 31, 2021

  503,768  $0.83   5.33  $1,954,882 
Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block]
  

Number of shares

  

Weighted average grant date fair value per share

 

Outstanding as of December 31, 2019

  303,150  $3.58 

Granted

  606,500   5.94 

Exercised

  (284,648)  3.64 

Forfeited or expired

  (109,650)  3.05 

Unvested as of December 31, 2020

  515,352  $6.12 

Granted

  1,119,323   11.68 

Vested

  (756,846)  9.71 

Forfeited

  (108,343)  8.03 

Unvested as of December 31, 2021

  769,486  $10.46 
Schedule of Stockholders' Equity Note, Warrants or Rights [Table Text Block]
  

Number of shares

  

Weighted average exercise price

  Weighted average remaining contractual life (years) 

Outstanding as of December 31, 2019

  500,739  $3.71   2.68 

Granted

         

Exercised

  (15,000)      

Forfeited or expired

         

Outstanding as of December 31, 2020

  485,739  $3.63   1.65 

Granted

         

Exercised

  (309,252)      

Forfeited or expired

         

Outstanding as of December 31, 2021

  176,487  $2.13   0.35