Note 9 - Shareholders' Equity - Information Related to Stock Options (Details)	12 Months Ended
	Dec. 31, 2021 $ / shares shares
Options outstanding, number of shares (in shares)	403,000
Options outstanding, weighted average remaining contractual life (Year)	6 years 9 months 21 days
options exercisable, number of shares (in shares)	324,800
Options exercisable, weighted average remaining contractual life (Year)	6 years 3 months 29 days
Exercise Price Range 1 [Member]
Exercise price (in dollars per share) | $ / shares	$ 0.98
Options outstanding, number of shares (in shares)	51,500
Options outstanding, weighted average remaining contractual life (Year)	1 year 11 months 15 days
options exercisable, number of shares (in shares)	51,500
Options exercisable, weighted average remaining contractual life (Year)	1 year 11 months 15 days
Exercise Price Range 2 [Member]
Exercise price (in dollars per share) | $ / shares	$ 1.91
Options outstanding, number of shares (in shares)	10,000
Options outstanding, weighted average remaining contractual life (Year)	9 years 3 months
options exercisable, number of shares (in shares)	3,333
Options exercisable, weighted average remaining contractual life (Year)	9 years 3 months
Exercise Price Range 3 [Member]
Exercise price (in dollars per share) | $ / shares	$ 2.21
Options outstanding, number of shares (in shares)	7,000
Options outstanding, weighted average remaining contractual life (Year)	9 years 5 months 12 days
options exercisable, number of shares (in shares)	2,333
Options exercisable, weighted average remaining contractual life (Year)	9 years 5 months 12 days
Exercise Price Range 4 [Member]
Exercise price (in dollars per share) | $ / shares	$ 2.68
Options outstanding, number of shares (in shares)	5,300
Options outstanding, weighted average remaining contractual life (Year)	9 years 10 months 13 days
options exercisable, number of shares (in shares)	1,767
Options exercisable, weighted average remaining contractual life (Year)	9 years 10 months 13 days
Exercise Price Range 5 [Member]
Exercise price (in dollars per share) | $ / shares	$ 2.89
Options outstanding, number of shares (in shares)	105,000
Options outstanding, weighted average remaining contractual life (Year)	8 years 10 months 13 days
options exercisable, number of shares (in shares)	51,667
Options exercisable, weighted average remaining contractual life (Year)	8 years 10 months 13 days
Exercise Price Range 6 [Member]
Exercise price (in dollars per share) | $ / shares	$ 2.92
Options outstanding, number of shares (in shares)	52,500
Options outstanding, weighted average remaining contractual life (Year)	7 years 1 month 17 days
options exercisable, number of shares (in shares)	47,500
Options exercisable, weighted average remaining contractual life (Year)	7 years 1 month 17 days
Exercise Price Range 7 [Member]
Exercise price (in dollars per share) | $ / shares	$ 3.00
Options outstanding, number of shares (in shares)	52,500
Options outstanding, weighted average remaining contractual life (Year)	7 years 7 months 13 days
options exercisable, number of shares (in shares)	47,500
Options exercisable, weighted average remaining contractual life (Year)	7 years 7 months 13 days
Exercise Price Range 8 [Member]
Exercise price (in dollars per share) | $ / shares	$ 3.30
Options outstanding, number of shares (in shares)	37,500
Options outstanding, weighted average remaining contractual life (Year)	5 years 9 months
options exercisable, number of shares (in shares)	37,500
Options exercisable, weighted average remaining contractual life (Year)	5 years 9 months
Exercise Price Range 9 [Member]
Exercise price (in dollars per share) | $ / shares	$ 3.50
Options outstanding, number of shares (in shares)	3,000
Options outstanding, weighted average remaining contractual life (Year)	6 years 9 months 3 days
options exercisable, number of shares (in shares)	3,000
Options exercisable, weighted average remaining contractual life (Year)	6 years 9 months 3 days
Exercise Price Range 10 [Member]
Exercise price (in dollars per share) | $ / shares	$ 4.10
Options outstanding, number of shares (in shares)	78,700
Options outstanding, weighted average remaining contractual life (Year)	6 years 2 months 23 days
options exercisable, number of shares (in shares)	78,700
Options exercisable, weighted average remaining contractual life (Year)	6 years 2 months 23 days