Run the preferred action immediately or choose a closely related alternative. The two Button halves share one outside shape; the attached Menu owns the alternatives.
Choose an alternative to make it the new main action; the main half then repeats it. The menu flips and edge-aligns only when viewport collision requires it.
| Example | Variant | Size | Usage |
|---|---|---|---|
| Primary | Small | The view’s single dominant action | |
| Secondary | Medium | Supporting action on a busy surface | |
| Secondary | Large | Roomier high-attention placement |
| Verdict | Rule |
|---|---|
| Do | Use one clear default and only close variations of that action. |
| Do | Update the main action’s name, icon, and behavior together after a choice. |
| Don’t | Mix unrelated commands or use a destructive action as the default. |
| Don’t | Round the inside corners or add local spacing between the halves. |