Note 12 - Stockholders' Equity - Summary of Warrants Outstanding (Details)	Dec. 31, 2020 $ / shares shares
Warrants outstanding (in shares)	1,244,974
First Set of Warrants Expiring September 2024 [Member]
Warrants outstanding (in shares)	5,000
Exercise Price (in dollars per share) | $ / shares	$ 0.30
Second Set of Warrants Expiring September 2024 [Member]
Warrants outstanding (in shares)	224,797
Exercise Price (in dollars per share) | $ / shares	$ 0.375
First Set of Warrants Expiring April 2024 [Member]
Warrants outstanding (in shares)	225,966
Exercise Price (in dollars per share) | $ / shares	$ 1.10
Second Set of Warrants Expiring April 2024 [Member]
Warrants outstanding (in shares)	111,931
Exercise Price (in dollars per share) | $ / shares	$ 1.375
Warrants Expiring March 2025 [Member]
Warrants outstanding (in shares)	316,584
Exercise Price (in dollars per share) | $ / shares	$ 2.50
Warrants Expiring February 2025 [Member]
Warrants outstanding (in shares)	269,496
Exercise Price (in dollars per share) | $ / shares	$ 3.125
Warrants Expiring March 2024 [Member]
Warrants outstanding (in shares)	80,286
Exercise Price (in dollars per share) | $ / shares	$ 3.125
Warrants Expiring December 2026 [Member]
Warrants outstanding (in shares)	10,914
Exercise Price (in dollars per share) | $ / shares	$ 22.99