The 9 points and 12 lines of <span class="mwe-math-element"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle \mathbb {Z} _{3}^{2}}"><semantics><mrow class="MJX-TeXAtom-ORD"><mstyle displaystyle="true" scriptlevel="0"><msubsup><mrow class="MJX-TeXAtom-ORD"><mi mathvariant="double-struck">Z</mi></mrow><mrow class="MJX-TeXAtom-ORD"><mn>3</mn></mrow><mrow class="MJX-TeXAtom-ORD"><mn>2</mn></mrow></msubsup></mstyle></mrow><annotation encoding="application/x-tex">{\displaystyle \mathbb {Z} _{3}^{2}}</annotation></semantics></math></span><img src="https://wikimedia.org/api/rest_v1/media/math/render/svg/7aed37d2cd0d41b29eb25def68732b2ff5a73bfb" class="mwe-math-fallback-image-inline" aria-hidden="true" style="vertical-align: -0.838ex; width:2.605ex; height:3.176ex;" alt="{\displaystyle \mathbb {Z} _{3}^{2}}"></span>, and a 4-element <a href="https://en.wikipedia.org/wiki/Cap_set" class="extiw" title="en:Cap set">cap set</a> (the four yellow points) in this space
<a href="//commons.wikimedia.org/wiki/User:David_Eppstein" class="mw-redirect" title="User:David Eppstein">David Eppstein</a>
<span class="int-own-work" lang="en">Own work</span>