week 11 and part of week 12

site/introwebdev/week-11-flexbox-2.html

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+[!]
+[=title "Week 11: Flexbox 2"]
+[=content-]
+<p>
+	If you haven't already, read <a href="week-8-flexbox-1.html">Flexbox 1</a>.
+</p>
+<p>
+	To complete our discussion of flexbox, we need to talk first about <i>axes</i>. The core idea is that a flexbox is
+	an <i>axis</i>: it puts content vertically or horizontally. It <i>can</i> violate this with <code>flex-wrap</code>,
+	but please don't do that. We say the axis along which content is distributed is the <b>primary axis</b>:
+	for default flexboxes, this is left/right (horizontal), but they can also be up/down (vertical).
+</p>
+<p>
+	You control the <i>primary</i> axis with the <code>flex-direction</code> property.
+	<code>flex-direction: row;</code> will set the flexbox' primary axis to horizontal,
+	and <code>flex-direction: column;</code> will set the flexbox' primary axis to vertical.
+	The <i>secondary axis</i> will always be the remaining option.
+</p>
+<p>
+	Along the secondary axis (up/down for a horizontal flexbox, left/right for a vertical flexbox), elements
+	may be centered, stretched, or justified to either end: you do this with the <code>align-items</code>
+	property. For instance, <code>align-items: center;</code> will bring all of the elements
+	to the center of the secondary axis. This is pretty useful for building centered layouts! 
+</p>
+<p>
+	Using <code>align-items: center; justify-content: center;</code> centers along both axes (remember, <code>justify-content</code> controls
+	the primary axis!), so for example:
+</p>
+<div style="border: 1px dashed white;display:flex;align-items:center;justify-content:center;height:200px;">
+<div style="background-color: red;">Content 1</div>
+<div style="background-color: blue;">Content 2</div>
+</div>
+<p>
+	Note that we can also force elements to stretch to fill up the secondary axis with
+	<code>align-items: stretch;</code>:
+</p>
+<div style="border: 1px dashed white;display:flex;align-items:stretch;justify-content:center;height:200px;">
+<div style="background-color: red;">Content 1</div>
+<div style="background-color: blue;">Content 2</div>
+</div>
+<p>
+	What if we want to mix the two? It turns out that we can do that with the
+	<code>align-self</code> property! Note that there is no <code>justify-self</code> property;
+	<code>align-self</code> works because of the assumption that there is only one element
+	at any point on the secondary axis (an assumption violated by <code>flex-wrap</code>, but we won't talk about that here).
+	If we do <code>align-self: center;</code> for the first element...
+</p>
+<div style="border: 1px dashed white;display:flex;align-items:stretch;justify-content:center;height:200px;">
+<div style="background-color: red;align-self: center;">Content 1</div>
+<div style="background-color: blue;">Content 2</div>
+</div>
+<p>
+	All three properties also support two strange values: <code>start</code> and <code>end</code>.
+	Doing <code>justify-content: end;</code> on the flexbox and <code>align-self: start;</code> on
+	the second content: 
+</p>
+<div style="border: 1px dashed white;display:flex;align-items:stretch;justify-content:end;height:200px;">
+<div style="background-color: red;align-self: center;">Content 1</div>
+<div style="background-color: blue;align-self: start;">Content 2</div>
+</div>
+<p>
+	Strange! <code>end</code> simply means "the furthest point across the axis" - which is usually
+	as far right (or as far down) as possible. <code>start</code> just means the opposite.
+</p>
+[/]
+[#template.html]