only one primitive: a painter. A painter draws its image within a frame.</li>
<li>We have means of combination: <code>rotate</code>, <code>beside</code>, and <code>below</code>.</li>
<li>Thanks to the closure property, we can build up complexity in this language quickly.</li>
<li>A frame is a parallelogram defined by an origin vector and two side vectors.</li>
<li>All frames are based on transformations from the unit square.</li>
<li>We can build primitive painters from lists of line segments.</li>
<li>A pa