While `Transform` lets you change the appearance of elements or groups of
elements, there might be occasions where you want to switch between a list of
behaviors based on some condition. This is analogous to a `switch` statement
or `if...else` statement in other languages.

For example, you might want to show a different background for early morning,
morning, lunch, afternoon, evening, and night.

`Condition` statements in Watch Face Format allow you to include different parts
of your watch face scene depending on the evaluation of expressions, for
example:  

    <Condition>
        <Expressions>
            <Expression name="is_early_morning">
                <![CDATA[[HOUR_0_23] >= 6 && [HOUR_0_23] < 8]]
            </Expression>
            <Expression name="is_morning">
                <![CDATA[[HOUR_0_23] < 12]]
            </Expression>
            ...
        </Expressions>
        <Compare expression="is_early_morning">
            <!-- Early morning content here -->
            <Group ... />
        </Compare>
        <Compare expression="is_morning">
            <!-- Morning content here -->
            <Group ... />
        </Compare>
        ...
        <!-- The "else" case -->
        <Default>
            <!-- content -->
        </Default>
    </Condition>

A few things to note about conditions:

1. The first `Compare` element where the `expression` is `true` is used, and others are ignored.
2. Owing to the XML format, it can often be easiest to wrap the expression definition in a `CDATA` element as shown here, as this avoids the need for XML escaping using entity elements such as `&gt;` and `&amp;`.
3. `Condition` structures can be nested.