Note 2 - The Company and Summary of Significant Accounting Policies (Details) - shares |
6 Months Ended | 12 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2019 |
Jun. 30, 2018 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Anti-dilutive securities | 39,416,352 | 3,390,120 | 8,682,368 | 1,164,905 |
| Exercise of common stock warrants | ||||
| Anti-dilutive securities | 1,813,053 | 0 | ||
| Conversion of preferred stock into common stock | ||||
| Anti-dilutive securities | 1,163,659 | 1,163,659 | ||
| Conversion of convertible debentures into common stock | ||||
| Anti-dilutive securities | 5,704,543 | 0 | ||
| Exercise of common stock options | ||||
| Anti-dilutive securities | 1,113 | 1,246 | ||