Consolidated Balance Sheets (Parentheticals) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020
Accounts receivable, allowance	$ 30	$ 62
Preferred stock, shares authorized (in shares)	5,000,000	5,000,000
Preferred stock, par value (in dollars per share)	$ 0.001	$ 0.001
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, shares authorized (in shares)	45,000,000	45,000,000
Common stock, par value (in dollars per share)	$ 0.001	$ 0.001
Common stock, shares issued (in shares)	27,323,000	25,110,000
Common stock, shares outstanding (in shares)	27,323,000	25,110,000