Note 7 - Stock Options - Changes in Options (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Options outstanding (in shares)	1,565,000	5,415,000
Options outstanding, weighted average exercise price (in dollars per share)	$ 0.85	$ 0.5
Options outstanding, aggregate intrinsic value	$ 0	$ 0	$ 0
Expired, options (in shares)	(500,000)	(3,850,000)
Expired, weighted average exercise price (in dollars per share)	$ 1.2	$ 0.36
Expired, aggregate intrinsic value (in dollars per share)	$ 0	$ 0
Options outstanding (in shares)	1,065,000	1,565,000
Options outstanding, weighted average exercise price (in dollars per share)	$ 0.69	$ 0.85