Note 5 - Share-based Compensation - Stock Options (Details) - USD ($)		3 Months Ended		12 Months Ended
		Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
2018 Equity Incentive Plan [Member]
Options outstanding, balance (in shares)		28,484,549	23,186,142	23,186,142
Weighted average exercise price per share, balance (in dollars per share)		$ 0.19	$ 0.19	$ 0.19
Options granted (in shares)		1,320,498	2,621,229
Exercise price per share, granted (in dollars per share)		$ 0.20
Weighted average exercise price per share, granted (in dollars per share)		$ 0.2	$ 0.23
Options Unvested (in shares)		(4,073,761)
Weighted average exercise price per share, unvested (in dollars per share)		$ 0.19
Options Vested (in shares)		25,731,286
Weighted average exercise price per share, vested (in dollars per share)		$ 0.19
Vested, aggregate intrinsic value	[1]	$ 678,000
Options outstanding, balance (in shares)		29,805,047	25,807,371	28,484,549
Weighted average exercise price per share, balance (in dollars per share)		$ 0.19	$ 0.19	$ 0.19
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)			0.12
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	0.40	0.40
Exercise price per share, granted (in dollars per share)			0.23
Exercise price per share, Unvested (in dollars per share)		0.32
Exercise price per share, Vested (in dollars per share)		0.43
Exercise price per share, balance (in dollars per share)		$ 0.43	$ 0.40	$ 0.43
The 2007 Equity Incentive Plan [Member]
Options outstanding, balance (in shares)		1,904,085	2,879,246	2,879,246
Weighted average exercise price per share, balance (in dollars per share)		$ 0.56	$ 0.49	$ 0.49
Options outstanding, balance (in shares)		1,904,085	2,879,246	1,904,085
Weighted average exercise price per share, balance (in dollars per share)		$ 0.56	$ 0.49	$ 0.56
Options outstanding, Expired (in shares)		0	0
Weighted average exercise price per share, Expired (in dollars per share)		$ 0	$ 0
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	0.23	0.28
Weighted average exercise price per share, Expired (in dollars per share)
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)
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	$ 0.39	$ 0.39
Options granted (in shares)		48,804	32,609
Exercise price per share, granted (in dollars per share)		$ 0.20	$ 0.23
Weighted average exercise price per share, granted (in dollars per share)		$ 0.20	$ 0.23
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)		18,565,133
Weighted average exercise price per share, vested (in dollars per share)		$ 0.38
Vested, aggregate intrinsic value	[2]	$ 88,000
Options outstanding, balance (in shares)		19,072,633	20,151,816	19,023,829
Weighted average exercise price per share, balance (in dollars per share)		$ 0.39	$ 0.39	$ 0.39
Non Plan [Member] | Minimum [Member]
Exercise price per share, balance (in dollars per share)		0.12	0.12	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
Non Plan [Member] | Maximum [Member]
Exercise price per share, balance (in dollars per share)		0.83	0.83	0.83
Exercise price per share, granted (in dollars per share)
Exercise price per share, Vested (in dollars per share)		0.83
Exercise price per share, balance (in dollars per share)		$ 0.83	$ 0.83	$ 0.83

[1] Aggregate intrinsic value based on closing common stock price of $0.20 at March 31, 2023.

[2] Aggregate intrinsic value based on closing common stock price of $0.18 at June 30, 2022.