Balance Sheets - USD ($)	Jun. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 8,471,914	$ 10,796,072
Accounts receivable, net of allowance of $502,251 and $398,847 in 2019 and 2018, respectively	4,997,148	5,021,111
Inventories, net	1,560,116	1,191,666
Prepaid expenses and other current assets	514,408	963,700
Total current assets	15,543,586	17,972,549
Property and equipment, net	297,494	343,693
Operating lease right-of-use assets	5,245,842
Other assets	168,153	198,365
Total assets	21,255,075	18,514,607
Current liabilities:
Accounts payable	1,642,049	1,726,360
Accrued liabilities	2,376,058	2,642,481
Deferred revenue	6,537,988	5,825,536
Current portion of operating lease liabilities	2,223,023
Total current liabilities	12,779,118	10,194,377
Long-term deferred revenue	508,772	407,151
Operating lease liabilities	3,048,650
Other liabilities	260,947	641,461
Total liabilities	16,597,487	11,242,989
Convertible preferred stock:
Convertible preferred stock, par value $0.001; 10,000,000 shares authorized, 23,855 and 23,900 shares outstanding at 2019 and 2018	5,948,953	5,960,475
Stockholders' equity (deficit):
Common stock, par value $0.001; 300,000,000 shares authorized, 59,383,038 and 59,058,297 shares issued at 2019 and 2018, respectively	59,383	59,058
Additional paid in capital	479,127,279	478,179,574
Treasury stock, 4,015 shares at 2019 and 2018	(205,999)	(205,999)
Accumulated deficit	(480,272,028)	(476,721,490)
Total stockholders' equity (deficit)	(1,291,365)	1,311,143
Total liabilities and stockholders' equity (deficit)	$ 21,255,075	$ 18,514,607