| In millions, except per share items | Dec-31-22 | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 |
| | 8-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Operating activities: | | | | | | | | |
| Net loss | | -16.2 | -25.2 | -21.5 | -20.4 | -24.1 | -19.7 | -24.0 |
| Adjustment to reconcile net loss to net cash used in operating activities: | | | | | | | | |
| Depreciation and amortization | | 0.0 | 0.0 | 0.0 | 0.1 | 0.1 | 0.1 | 0.2 |
| Stock compensation expense | | 0.6 | 0.4 | 1.0 | 1.1 | 1.7 | 3.9 | 3.8 |
| Changes in assets and liabilities: | | | | | | | | |
| Receivables | | 0.0 | 0.1 | -0.1 | 0.0 | 0.0 | 1.5 | -1.4 |
| Prepaid expenses and other current assets | | 0.5 | -0.1 | 0.1 | 0.1 | 0.8 | 0.2 | 1.2 |
| Accounts payable | | -2.1 | 0.6 | 0.2 | -1.5 | 0.9 | 1.9 | -0.6 |
| Accrued expenses and other current liabilities | | -1.8 | 1.2 | -0.4 | | | | |
| Deferred revenue | | -0.2 | -0.2 | -0.2 | -0.4 | -0.5 | | |
| Net cash used in operating activities | | -19.5 | -23.1 | -20.8 | -22.7 | -23.8 | -15.8 | |
| |
| Financing activities: | | | | | | | | |
| Proceeds from the sale of common stock and warrants, net of costs | | | | | | | | |
| Net cash provided by financing activities | | | | | | | | |
| Effect of foreign currency translation on cash | | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 | | |
| Cash and cash equivalents at beginning of period | | | | | | | 19.8 | 43.6 |
| Cash and cash equivalents at end of period | | | | | | | | 19.8 |