Contextual Tools can be revealed progressively with Multi-Level Tools. Songza provides a set of tools that get revealed after a user clicks on a song. Additional tools are revealed when hovering over the newly visible tools (Figure 4-21).
Songza reveals the four options "play", "rate", "share", and "add to playlist" after the user clicks on a song title. Hovering over "share" or "rate" reveals a secondary set of menu items (Figure 14-21, center).
Radial menus such as in Songza have been shown to have some advantages over more traditional menus. First, experienced users can rely on muscle memory rather than having to look directly at the menu items. Second, the proximity and targeting size make the menu easy to navigate since the revealed menu items are all equally close at hand (recall Fitts's Law).
The one potential downside to this approach is that rating a song requires several steps: an initial click on the song, moving the mouse over the "rate" menu item, then clicking either the thumbs up or thumbs down option. If rating songs was an important activity, the extra effort might prevent some users from doing so. An alternate approach would be to replace "rate" directly with the thumbs up and the thumbs down options.
Another interesting decision Songza made was to not activate the radial menu on hover. Instead, the user must click on a song to reveal the menu. Activating on click makes the user intent more explicit.
Making activation more explicit avoids the issues described earlier in the Hover and Cover anti-pattern. The user has chosen to interact with the song. Conversely, with a mouse hover, it's never quite clear if the user meant to activate the menu or just happened to pause over a song title.
However, this does mean there is no way to start a song playing with just a simple click. Playing a song requires moving to the top leaf. One possible solution would be to place the "play" option in the middle of the menu (at the stem) instead of in one of the leaves. Clicking once would activate the menu. Clicking a second time (without moving the mouse) would start playing the song. This interaction is very similar to one commonly used in desktop applications: allowing a double-click to activate the first item (default action) in a right-click menu.
Keep the most common actions as near to the activation point as possible.
Picnik is an online photo-editing tool that integrates with services like Flickr. In all, there are six sets of tools, each with a wide range of palette choices. Picnik uses Multiple-Level Tools to expose additional functionality. By wrapping the photo with tools in context and progressively revealing the levels of each tool, Picnik makes editing straightforward (Figure 4-22).
Another variation on Multi-Level Tools is the "mutton" (menu + button = mutton). Muttons are useful when there are multiple actions and we want one of the actions to be the default. Yahoo! Mail uses a mutton for its "Reply" button (Figure 4-23).
Figure 4-23. Yahoo! Mail's "Reply" button looks like a drop-down when hovered over; clicking "Reply" replies to sender, and clicking the drop-down offers the default action as well as "Reply to All"
Clicking "Reply" performs the individual reply. To reply to all, the menu has to be activated by clicking on the drop-down arrow to show the menu.
Muttons are used to:
Provide a default button action ("Reply to Sender")
Provide a clue that there are additional actions
Provide additional actions in the drop-down
If muttons are not implemented correctly, they can be problematic for those using accessibility technologies. Because an earlier version of Yahoo! Mail did not make the mutton keyboard accessible, Yahoo!'s accessibility guru, Victor Tsaran, was convinced that there was no "Reply to All" command in the Yahoo! Mail interface. Only after the mutton was made more accessible could he find the "Reply" command.
At the beginning of this chapter, we discussed Fitts's Law. Recall that the time it takes to acquire a target is a function of both distance and size. Even if tools are placed close by in context, don't forget to make them large enough to target.
Both Flickr and Yahoo! Mail provide a reasonable-size target for the drop-down arrow. Compare this with the expand/collapse arrow used in an early version of Yahoo! for Teachers (Figure 4-24).
The arrow is tiny (8×8 pixels). It is exposed only on hover. Providing Tiny Targets makes interaction much more difficult. An alternate approach would be to always show a "more info" link. Clicking it could toggle the additional profile information. Alternatively, providing a larger target for the arrow would improve its findability and targeting.
 Aza Raskin is the designer of Songza, founder of Humanized. He is the son of the late human-computer interface expert Jef Raskin.
 Also known as pie menus. See Jack Callahan et al. (1988), "An empirical comparison of pie vs. linear menus." Proceedings of ACM CHI Conference on Human Factors in Computing Systems: 95–100.