The _alpha control adjusts the transparency of your selected control. This property is a an expression of a percent of opacity.

An _alpha value of 100 is fully opaque (i.e. not transparent at all).  At the other extreme, an _alpha value of 0 makes the control completely invisible.  (That might not seem too useful at first, but sometimes it is useful to make a control disappear when it would not be appropriate for the user to be able to click on it.) 

There are a lot of cool visual effects that you can get by using _alpha values that are in the mid range.  Compare the screen shot below with that of the previous page of this tutorial. Notice that, at _alpha = 50, the color of the Pushbutton has changed, and the lettering looks somewhat washed out, making it appear that this Control is disabled.

Note that we had to check the _alpha checkbox above the SpinEdit control before we were able to even adjust the value of _alpha away from its default value of 100 (percent).

We will have much more to say about how and when to use _alpha transparency as we go along.

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