Note 5 - Share-based Compensation - Stock Options (Details) - USD ($)		9 Months Ended		12 Months Ended
		Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
2018 Equity Incentive Plan [Member]
Options outstanding, balance (in shares)		28,484,549	23,186,142	23,186,142
Options granted (in shares)		8,219,920	4,748,212
Options Unvested (in shares)		(4,648,922)
Options Vested (in shares)		32,055,547
Vested, September 30, 2023	[1]	$ 278,000
Options outstanding, balance (in shares)		36,704,469	27,934,354	28,484,549
2018 Equity Incentive Plan [Member] | Minimum [Member]
Exercise price per share, balance (in dollars per share)		$ 0.12	$ 0.16	$ 0.16
Exercise price per share, granted (in dollars per share)		0.17	0.18
Exercise price per share, Unvested (in dollars per share)		0.12
Exercise price per share, Vested (in dollars per share)		0.12
Exercise price per share, balance (in dollars per share)		0.12	0.12	0.12
2018 Equity Incentive Plan [Member] | Maximum [Member]
Exercise price per share, balance (in dollars per share)		0.43	0.43	0.43
Exercise price per share, granted (in dollars per share)		0.2	0.27
Exercise price per share, Unvested (in dollars per share)		0.27
Exercise price per share, Vested (in dollars per share)		0.43
Exercise price per share, balance (in dollars per share)		0.43	0.43	0.43
2018 Equity Incentive Plan [Member] | Weighted Average [Member]
Weighted average exercise price per share, balance (in dollars per share)		0.19	0.19	0.19
Weighted average exercise price per share, granted (in dollars per share)		0.18	0.22
Weighted average exercise price per share, unvested (in dollars per share)		0.15
Weighted average exercise price per share, vested (in dollars per share)		0.19
Weighted average exercise price per share, balance (in dollars per share)		$ 0.19	$ 0.19	$ 0.19
The 2007 Equity Incentive Plan [Member]
Options outstanding, balance (in shares)		1,904,085	2,879,246	2,879,246
Options outstanding, balance (in shares)		1,564,085	1,904,085	1,904,085
Options outstanding, Expired (in shares)		(340,000)	(975,161)
The 2007 Equity Incentive Plan [Member] | Minimum [Member]
Weighted average exercise price per share, balance (in dollars per share)		$ 0.28	$ 0.23	$ 0.23
Weighted average exercise price per share, balance (in dollars per share)		0.28	0.24	0.28
Weighted average exercise price per share, Expired (in dollars per share)		0.28	0.28
The 2007 Equity Incentive Plan [Member] | Maximum [Member]
Weighted average exercise price per share, balance (in dollars per share)		0.69	0.94	0.94
Weighted average exercise price per share, balance (in dollars per share)		0.69	0.94	0.69
Weighted average exercise price per share, Expired (in dollars per share)		0.3	0.35
The 2007 Equity Incentive Plan [Member] | Weighted Average [Member]
Weighted average exercise price per share, balance (in dollars per share)		0.56	0.49	0.49
Weighted average exercise price per share, balance (in dollars per share)		0.61	0.56	$ 0.56
Weighted average exercise price per share, Expired (in dollars per share)		$ 0.3	$ 0.36
Non Plan [Member]
Options outstanding, balance (in shares)		19,023,829	20,119,207	20,119,207
Weighted average exercise price per share, balance (in dollars per share)		$ 0.39	$ 0.41	$ 0.41
Options granted (in shares)		60,040	105,797
Weighted average exercise price per share, granted (in dollars per share)		$ 0.2	$ 0.26
Options Unvested (in shares)		(507,500)
Exercise price per share, Unvested (in dollars per share)		$ 0.45
Weighted average exercise price per share, unvested (in dollars per share)		$ 0.45
Options Vested (in shares)		17,370,819
Weighted average exercise price per share, vested (in dollars per share)		$ 0.39
Vested, September 30, 2023	[1]	$ 28,000
Options outstanding, balance (in shares)		17,878,319	20,225,004	19,023,829
Weighted average exercise price per share, balance (in dollars per share)		$ 0.39	$ 0.39	$ 0.39
Options outstanding, Expired (in shares)		(1,205,550)
Weighted average exercise price per share, Expired (in dollars per share)		$ 0.3
Exercise price per share, Expired (in dollars per share)		0.3
Non Plan [Member] | Minimum [Member]
Exercise price per share, balance (in dollars per share)		0.12	0.17	0.17
Exercise price per share, granted (in dollars per share)		0.18	0.23
Exercise price per share, Vested (in dollars per share)		0.12
Exercise price per share, balance (in dollars per share)		0.12	0.17	0.12
Non Plan [Member] | Maximum [Member]
Exercise price per share, balance (in dollars per share)		0.83	1	1
Exercise price per share, granted (in dollars per share)		0.2	0.27
Exercise price per share, Vested (in dollars per share)		0.83
Exercise price per share, balance (in dollars per share)		$ 0.83	$ 1	$ 0.83

[1] Aggregate intrinsic value based on closing common stock price of $0.17 at September 30, 2023.