Note 10 - Preferred Stock and Common Stock Warrants - Fair Value Assumptions (Details)	Dec. 31, 2020	Dec. 31, 2019
Measurement Input, Share Price [Member]
Warrant measurement input	2.09	6.14
Measurement Input, Exercise Price [Member]
Warrant measurement input	0.01	0.01
Measurement Input, Risk Free Interest Rate [Member]
Warrant measurement input	0.001	0.016
Measurement Input, Price Volatility [Member]
Warrant measurement input	0.586	0.276
Measurement Input, Expected Term [Member]
Warrant measurement input	0.8	1.8