class="t"><span class="str">        edges = (top, right, bottom, left).</span>&nbsp;</span><span class="r"></span></p>
    <p class="pln"><span class="n"><a id="t58" href="#t58">58</a></span><span class="t"><span class="str">                corner c0 is formed by edges top + left => edges[0] &amp; edges[3]</span>&nbsp;</span><span class="r"></span></p>
    <p class="pln"><span class="n"><a id="t59" href="#t59">59</a></span><span class="t"><span class="str">                corner c1 => top + right => edges[0