Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 69,466	$ 39,181
Short-term investments	78,016	51,508
Accounts receivable, net of allowances of $13 and $45 at December 31, 2020 and 2019, respectively	9,070	8,601
Inventories	9,989	10,322
Prepaid expenses and other current assets	6,787	2,878
Total current assets	173,328	112,490
Long-term investments	0	18,224
Property and equipment, net	2,844	2,734
Restricted cash	310	310
Other non-current assets	2,832	3,644
Total assets	179,314	137,402
Current liabilities:
Accounts payable	2,598	1,898
Accrued liabilities	16,957	15,034
Total current liabilities	19,555	16,932
Long-term debt	48,533	44,879
Other liabilities	3,726	3,700
Total liabilities	71,814	65,511
Commitments and contingencies (Note 7)
Preferred stock, $0.001 par value
Shares authorized: 5,000,000 at December 31, 2020 and 2019	0	0
Common stock, $0.001 par value
Shares issued and outstanding: 34,249,649 and 31,255,267 at December 31, 2020 and 2019, respectively	34	31
Additional paid-in capital	346,318	263,384
Accumulated other comprehensive income	39	2
Accumulated deficit	(238,891)	(191,526)
Total stockholders’ equity	107,500	71,891
Total liabilities and stockholders’ equity	$ 179,314	$ 137,402