| In millions, except per share items | Dec-31-21 | Dec-31-20 | Dec-31-19 | Dec-31-18 | Dec-31-17 | Dec-31-16 | Dec-31-15 | Dec-31-14 |
| | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K | 10-K |
| Revenue | 13.6 | 11.3 | 3.3 | 9.1 | 9.9 | 3.4 | 4.0 | 3.5 |
| Revenue growth | 20.4% | 244.4% | -63.9% | -8.2% | 192.2% | -16.0% | 14.1% | |
| Cost of revenue | 5.3 | 5.0 | 3.0 | | | | | |
| Gross profit | 8.3 | 6.3 | 0.3 | 3.7 | 5.1 | 0.6 | 1.5 | 0.6 |
| Gross margin | 61.4% | 55.4% | 10.1% | 40.4% | 51.3% | 17.2% | 38.0% | 17.7% |
| |
| Operating expenses: | | | | | | | | |
| Sales and marketing | 33.6 | 15.2 | 16.7 | 29.9 | 28.8 | 10.2 | 3.5 | 4.7 |
| General and administrative | 24.4 | 10.5 | | | | | | |
| Research and development | 2.5 | 3.5 | 6.9 | 10.7 | 10.6 | 9.9 | 13.0 | 5.8 |
| Total operating expenses | 64.8 | 18.7 | 23.6 | 40.6 | 39.5 | 20.1 | 16.5 | 10.5 |
| Operating loss | -56.5 | -12.5 | -23.2 | -37.0 | -34.4 | -19.5 | -14.9 | -9.8 |
| Operating margin | -415.4% | -110.2% | -708.0% | -406.2% | -346.9% | -574.9% | -369.7% | -278.0% |
| |
| Other expense (income), net: | | | | | | | | |
| Interest income, net | -0.8 | -2.0 | -0.4 | -0.2 | -0.1 | -0.5 | -0.5 | -0.2 |
| Gain on changes in fair value of liability warrants | | | | | | -0.5 | 0.0 | 0.2 |
| (Gain) loss on foreign currency exchange, net | -0.2 | -0.4 | | | | | | |
| Other | | | -0.1 | -0.2 | -0.2 | 0.0 | 0.0 | 0.0 |
| Loss before income tax provision | -62.0 | -21.8 | | | | | | |
| Income tax expense | -0.1 | -0.2 | | | | | | |
| Net loss | -61.9 | -21.6 | -23.7 | -37.4 | -34.8 | -20.5 | -15.6 | -9.9 |
| |
| Net loss per share - basic and diluted: | | | | | | | | |
| Net loss per share - basic (in dollars per share) | ($5.00) | ($5.54) | ($5.03) | ($19.64) | ($2.08) | ($4.85) | ($27.14) | ($18.61) |
| Net loss per share - diluted (in dollars per share) | ($5.00) | ($5.54) | ($5.03) | ($19.64) | ($2.08) | ($4.85) | ($27.14) | ($18.61) |
| |
| Shares used to compute basic net loss per share (in shares) | 12.4 | 3.9 | 4.7 | 1.9 | 16.7 | 4.2 | 0.6 | 0.5 |
| Shares used to compute diluted net loss per share (in shares) | 12.4 | 3.9 | | | | | | |