Balance Sheets - USD ($)	Jun. 30, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 44,006,162	$ 30,182,115
Accounts receivable, net of allowance of $412,813 and $380,212 at 2020 and 2019, respectively	3,041,100	5,329,577
Inventories, net	4,576,078	1,847,530
Prepaid expenses and other current assets	1,611,504	1,470,922
Total current assets	53,234,844	38,830,144
Property and equipment, net	263,039	250,443
Operating lease right-of-use assets	3,282,783	4,286,064
Other assets	269,542	218,103
Total assets	57,050,208	43,584,754
Current liabilities:
Short-term debt	2,158,310
Accounts payable	1,571,679	2,099,097
Accrued liabilities	2,401,625	2,721,104
Deferred revenue	5,456,595	5,092,455
Current portion of operating lease liabilities	2,265,546	2,248,189
Total current liabilities	13,853,755	12,160,845
Long-term deferred revenue	508,772	554,258
Operating lease liabilities	1,069,090	2,089,537
Other liabilities	255,517	255,517
Total liabilities	15,687,134	15,060,157
Series A - Convertible preferred stock:
Convertible preferred stock, Series A, par value $0.001; 22,813 and 23,110 shares outstanding at 2020 and 2019, respectively	5,682,141	5,758,190
Stockholders’ equity:
Convertible preferred stock, Series B, par value $0.001; 10,000,000 shares authorized, 5,610,121 shares outstanding at 2020 and 2019	5,610	5,610
Common stock, par value $0.001; 300,000,000 shares authorized, 73,030,824 and 68,529,623 shares issued at 2020 and 2019, respectively	73,031	68,530
Additional paid in capital	521,013,702	504,211,040
Treasury stock, 4,015 shares at 2020 and 2019	(205,999)	(205,999)
Accumulated deficit	(485,205,411)	(481,312,774)
Total stockholders’ equity	35,680,933	22,766,407
Total liabilities and stockholders’ equity	$ 57,050,208	$ 43,584,754