Note 8 - Stock-based Compensation Expense - Summary of Stock Option Activity (Details) - USD ($)	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021	Jan. 01, 2022
Balance (in shares)	95,000	67,000
Balance, grant date weighted-average exercise price (in dollars per share)	$ 2.76	$ 2.72
Balance, weighted average remaining contractual life (Year)	5 years 5 months 8 days	4 years 9 months 29 days	3 years 3 months 29 days
Balance, aggregate intrinsic value	$ 0	$ 25,000		$ 0
Granted (in shares)	70,000	50,000
Granted, grant date weighted-average exercise price (in dollars per share)	$ 2.89	$ 2.72
Granted, weighted average remaining contractual life (Year)	7 years	7 years
Exercised (in shares)	0	(4,000)
Exercised, grant date weighted-average exercise price (in dollars per share)		$ 2.29
Forfeited (in shares)	(19,000)	(18,000)
Forfeited, grant date weighted-average exercise price (in dollars per share)	$ 2.69	$ 2.64
Balance (in shares)	146,000	95,000	67,000
Balance, grant date weighted-average exercise price (in dollars per share)	$ 2.83	$ 2.76	$ 2.72
Exercisable (in shares)	31,000	38,000
Exercisable, grant date weighted-average exercise price (in dollars per share)	$ 2.84	$ 2.79
Exercisable, weighted average remaining contractual life (Year)	3 years 4 months 17 days
Minimum [Member]
Exercisable, weighted average remaining contractual life (Year)		2 years 4 months 17 days