Note 6 - Stockholders' Equity - Summary of Option Activity (Details) - USD ($)	9 Months Ended	12 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Aggregate intrinsic value, outstanding		$ 1,083
Share-Based Payment Arrangement, Option [Member] | Share-Based Payment Arrangement, Employee [Member]
Options outstanding, balance (in shares)	3,059,989
Weighted average exercise price, outstanding (in dollars per share)	$ 2.36
Weighted average remaining contractual life, outstanding (Year)	5 years 7 months 28 days	6 years 4 months 17 days
Granted, options (in shares)	0
Weighted average exercise price, granted (in dollars per share)	$ 0
Exercised, options (in shares)	0
Weighted average exercise price, exercised (in dollars per share)	$ 0
Forfeited and expired, options (in shares)	(18,000)
Weighted average exercise price, forfeited or expired (in dollars per share)	$ 0
Options outstanding, balance (in shares)	3,041,989	3,059,989
Weighted average exercise price, outstanding (in dollars per share)	$ 2.29	$ 2.36
Exercisable, options (in shares)	1,469,651
Weighted average exercise price, exercisable (in dollars per share)	$ 2.37
Weighted average remaining contractual life, exercisable (Year)	4 years 11 months 19 days
Share-Based Payment Arrangement, Option [Member] | Share-Based Payment Arrangement, Nonemployee [Member]
Options outstanding, balance (in shares)	91,663
Weighted average exercise price, outstanding (in dollars per share)	$ 1.75
Weighted average remaining contractual life, outstanding (Year)	2 years 3 months	2 years 6 months 18 days
Granted, options (in shares)	8,333
Weighted average exercise price, granted (in dollars per share)	$ 0.89
Forfeited and expired, options (in shares)	(8,333)
Weighted average exercise price, forfeited or expired (in dollars per share)	$ 0.75
Options outstanding, balance (in shares)	91,663	91,663
Weighted average exercise price, outstanding (in dollars per share)	$ 1.76	$ 1.75
Exercisable, options (in shares)	77,776
Weighted average exercise price, exercisable (in dollars per share)	$ 1.89
Weighted average remaining contractual life, exercisable (Year)	1 year 11 months 4 days
Aggregate intrinsic value, outstanding	$ 8,000
Weighted average remaining contractual life, granted (Year)	4 years 5 months 15 days
Aggregate intrinsic value, exercisable	$ 6,777