Note 5 - Share-based Compensation - Stock Options (Details) - $ / shares		3 Months Ended		9 Months Ended
	Jun. 29, 2018	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2018	Sep. 30, 2017
The 2007 Equity Incentive Plan [Member]
Options outstanding, granted (in shares)					340,000
Weighted average price per share, granted (in dollars per share)					$ 0.65
Options outstanding, ending balance (in shares)		9,721,586	9,721,586	9,721,586	10,256,586
Weighted average price per share, ending balance (in dollars per share)		$ 0.43	$ 0.43	$ 0.43	$ 0.44
Options outstanding, Balance (in shares)				9,831,586	9,916,586
Weighted average price per share, Balance (in dollars per share)		0.43	0.43	$ 0.44	$ 0.44
Options outstanding, expired (in shares)				(110,000)
Weighted average price per share, expired (in dollars per share)				$ 1.60
Weighted average price per share, beginning balance (in dollars per share)				0.44	0.44
The 2007 Equity Incentive Plan [Member] | Minimum [Member]
Exercise price per share, granted (in dollars per share)					0.39
Exercise price per share, ending balance (in dollars per share)		0.23	0.23	0.23	0.23
Exercise price per share, Balance (in dollars per share)		0.23	0.23	0.23	0.23
Exercise price per share,Expired (in dollars per share)				0.99
Exercise price per share, beginning balance (in dollars per share)				0.23	0.23
The 2007 Equity Incentive Plan [Member] | Maximum [Member]
Exercise price per share, granted (in dollars per share)					0.69
Exercise price per share, ending balance (in dollars per share)		1.65	1.65	1.65	1.89
Exercise price per share, Balance (in dollars per share)		$ 1.65	$ 1.65	1.89	1.89
Exercise price per share,Expired (in dollars per share)				1.89
Exercise price per share, beginning balance (in dollars per share)				$ 1.89	$ 1.89
Outside of the 2007 Plan [Member]
Options outstanding, granted (in shares)				1,211,527	6,828,872
Weighted average price per share, granted (in dollars per share)				$ 0.26	$ 0.46
Options outstanding, ending balance (in shares)		18,829,935	18,829,935	18,829,935	19,244,379
Weighted average price per share, ending balance (in dollars per share)		$ 0.45	$ 0.45	$ 0.45	$ 0.51
Options outstanding, Balance (in shares)				20,018,408	20,148,766
Weighted average price per share, Balance (in dollars per share)		0.45	0.45	$ 0.51	$ 0.43
Options outstanding, expired (in shares)				(2,400,000)	(3,866,629)
Exercise price per share,Expired (in dollars per share)				$ 0.99	$ 0.18
Weighted average price per share, expired (in dollars per share)				0.99	0.18
Weighted average price per share, beginning balance (in dollars per share)				0.51	$ 0.43
Options outstanding, exercised (in shares)					(3,866,630)
Exercised (in dollars per share)					$ 0.18
Weighted average price per share, exercised (in dollars per share)					0.18
Outside of the 2007 Plan [Member] | Minimum [Member]
Exercise price per share, granted (in dollars per share)				0.23	0.43
Exercise price per share, ending balance (in dollars per share)		0.25	0.25	0.25	0.18
Exercise price per share, Balance (in dollars per share)		0.25	0.25	0.25	0.18
Exercise price per share, beginning balance (in dollars per share)				0.25	0.18
Outside of the 2007 Plan [Member] | Maximum [Member]
Exercise price per share, granted (in dollars per share)				0.43	0.67
Exercise price per share, ending balance (in dollars per share)		1	1	1	1
Exercise price per share, Balance (in dollars per share)		$ 1	$ 1	1	1
Exercise price per share, beginning balance (in dollars per share)				$ 1	$ 1
2018 Equity Incentive Plan [Member]
Options outstanding, granted (in shares)	296,976	493,111	790,087
Weighted average price per share, granted (in dollars per share)	$ 0.43		$ 0.34
Options outstanding, ending balance (in shares)		790,087	790,087	790,087
Weighted average price per share, ending balance (in dollars per share)		$ 0.34	$ 0.34	$ 0.34
Weighted average price per share, Balance (in dollars per share)		0.34	0.34	0.34
2018 Equity Incentive Plan [Member] | Minimum [Member]
Exercise price per share, granted (in dollars per share)			0.25
Weighted average price per share, granted (in dollars per share)		0.25
Exercise price per share, ending balance (in dollars per share)		0.25	0.25	0.25
Exercise price per share, Balance (in dollars per share)		0.25	0.25	0.25
2018 Equity Incentive Plan [Member] | Maximum [Member]
Weighted average price per share, granted (in dollars per share)		0.31	0.43
Weighted average price per share, ending balance (in dollars per share)		0.43	0.43	0.43
Weighted average price per share, Balance (in dollars per share)		$ 0.43	$ 0.43	$ 0.43