Note 6 - Warrants and Registration Rights Agreements - Summary of the Warrants Issued and Changes (Details)	6 Months Ended
	Jun. 30, 2021 $ / shares shares
Outstanding, beginning balance (in shares) | shares	6,034,702
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 0.07
Granted (in shares) | shares	0
Granted, weighted average exercise price (in dollars per share) | $ / shares	$ 0
Canceled / Expired (in shares) | shares	(500,000)
Canceled / expired, weighted average exercise price (in dollars per share) | $ / shares	$ 0
Exercised (in shares) | shares	(1,034,702)
Exercised, weighted average exercise price (in dollars per share) | $ / shares	$ 0
Outstanding, ending balance (in shares) | shares	4,500,000
Outstanding, weighted average exercise price (in dollars per share) | $ / shares	$ 0.01