I remember playing with this.<p>Making electronics can be pretty fun. <a href="http:&#x2F;&#x2F;powdertoy.co.uk&#x2F;Browse&#x2F;View.html?ID=915343" rel="nofollow">http:&#x2F;&#x2F;powdertoy.co.uk&#x2F;Browse&#x2F;View.html?ID=915343</a><p>(It&#x27;s not actually an ALU. All it does is add or subtract. But it was the best of its time!)