Note 7 - Stock Purchase Warrants (Details Textual) - USD ($)		1 Months Ended		3 Months Ended						12 Months Ended
	Jan. 01, 2020	Dec. 31, 2021	Dec. 31, 2020	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Nov. 30, 2021	Nov. 30, 2020	Oct. 31, 2020	Sep. 17, 2018
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 0.15	$ 0.49							$ 0.15	$ 0.49	$ 0.55	$ 0.56
Class of Warrant or Right, Outstanding, Weighted Average Remaining Contractual Term (Year)										1 year 8 months 15 days	2 years 8 months 1 day	1 year 8 months 23 days	2 years 6 months 3 days
Share-based Payment Arrangement, Expense				$ 0	$ 0	$ 0	$ 0	$ 0	$ 0
Warrant Modification, Amount										$ 795,592	$ (0)	$ (0)
Class of Warrant or Right, Exercised During Period (in shares)										(6,865,461)	233,333	0
Warrants Issued with the 2018 Convertible Notes [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 0.15								$ 0.15
Class of Warrant or Right, Outstanding, Weighted Average Remaining Contractual Term (Year)										1 year 9 months
Class of Warrant or Right, Outstanding, Aggregate Intrinsic Value		$ 0								$ 0
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)																	466,666
Class of Warrant or Right, Exercised During Period (in shares)	233,333
Stock Issued During Period, Shares, Exercise of Warrants (in shares)											1,022,857
Warrants Issued with 2019 Senior Secured Notes [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)												$ 0.15				$ 0.40
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)												457,500				3,977,971
Warrants and Rights Outstanding, Term (Year)												2 years				5 years
Warrants and Rights Outstanding												$ 17,763
Warrants Issued to Employees [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)																$ 0.40
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)																2,887,500
Warrants and Rights Outstanding, Term (Year)																5 years
Modified Warrants [Member]
Class of Warrant or Right, Exercise Price of Warrants or Rights (in dollars per share)		$ 0.20	$ 0.20							$ 0.20	$ 0.20			$ 0.40	$ 0.40
Class of Warrant or Right, Number of Securities Called by Warrants or Rights (in shares)															6,865,461
Share-based Payment Arrangement, Expense		$ 13,936	$ 13,936
Warrant Modification, Amount		$ 795,592	$ 795,592
Stock Issued During Period, Shares, Exercise of Warrants (in shares)		6,865,461