Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets
Cash and cash equivalents	$ 16,966	$ 15,139
Accounts receivable, net of allowances of $26 and $26, respectively	15	245
Costs and estimated earnings in excess of billings on uncompleted contracts	680	125
Inventory	4,541	1,233
Other current assets	945	606
Total current assets	23,147	17,348
Property and equipment, net	3,251	1,537
Restricted cash	435	435
Intangible assets	602	718
Other assets	2,262	68
Total assets	29,697	20,106
Current liabilities
Accounts payable	3,063	2,195
Accrued liabilities	5,864	3,704
Deferred revenue	999	999
Billings on uncompleted contracts in excess of related costs	5	168
Other current liabilities	10,142	178
Total current liabilities	20,073	7,244
Deferred revenue, net of current portion	4,151	5,150
Deferred rent, net of current portion	302	185
Other long-term liabilities	305	53
Total liabilities	24,831	12,632
Commitments and contingencies (Note 11)
Shareholders' equity (deficit)
Preferred stock, par value $0.001; 25,000 shares authorized; 0 and 0 shares issued and outstanding	0	0
Common stock, par value $0.001; 100,000 shares authorized; 78,597 and 68,093 shares issued and outstanding at December 31, 2017 and 2016, respectively	79	68
Additional paid-in capital	528,873	507,249
Accumulated deficit	(524,086)	(499,843)
Total shareholders' equity (deficit)	4,866	7,474
Total liabilities and shareholders' equity (deficit)	$ 29,697	$ 20,106