| In millions, except per share items | Dec-31-22 | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 |
| | 8-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Cash flows from operating activities: | | | | | | |
| Net loss | | -11.8 | -12.7 | -12.0 | -67.4 | -25.7 |
| Adjustments to reconcile net loss to net cash used in operating activities: | | | | | | |
| Stock-based compensation | | 1.3 | 1.0 | 0.1 | 2.8 | |
| Depreciation and amortization | | 0.1 | 0.1 | | | |
| Change in fair value of warrant liabilities | | 0.0 | 0.0 | 0.3 | 0.2 | |
| Changes in operating assets and liabilities: | | | | | | |
| Accounts receivable | | -0.1 | 0.0 | 0.0 | -0.1 | 0.0 |
| Inventories | | -2.1 | 0.0 | -1.3 | -0.7 | -0.4 |
| Prepaid expenses and other assets | | -0.2 | 0.1 | -0.5 | -0.2 | -0.1 |
| Accounts payable | | 0.9 | -0.9 | 1.0 | -0.8 | 0.3 |
| Accrued liabilities | | 0.0 | 0.3 | 0.3 | 0.1 | -1.4 |
| Net cash used in operating activities | | -11.5 | -9.9 | -11.0 | -10.0 | -10.4 |
| |
| Cash flows from investing activities: | | | | | | |
| Purchases of property and equipment | | -0.1 | -0.1 | 0.0 | | -0.1 |
| Net cash used in investing activities | | -0.1 | -0.1 | 0.0 | -0.1 | -0.2 |
| |
| Cash flows from financing activities: | | | | | | |
| Repayment of convertible note payable | | | -2.2 | | -0.2 | -5.1 |
| Proceeds from exercise of warrants | | | 0.8 | 1.2 | | |
| Net cash provided by (used in) financing activities | | 17.3 | 17.0 | 8.1 | 13.0 | 10.7 |
| |
| Supplemental disclosure of cash flow information: | | | | | | |
| Cash paid for interest | | 0.0 | 0.4 | | | |
| Cash paid for income taxes | | 0.0 | 0.0 | 0.0 | 0.0 | 0.0 |
| Noncash Investing and Financing Activities: | | | | | | |