Term for something that appears complex but is actually very simple

Solution 1:

We call a thing which is actually simple but appears complex deceptively complex. Both OALD and CALD call something which is actually complex but appears simple deceptively simple.

Solution 2:

A 'ruse' is meant to deceive, to hide the truth, possibly by making something appear more complex than it is. Ruse does not explicitly relate to complexity vs. simplicity, but it does relate to the subjective perspective of the person: they are being deceived by a trick that can easily be exposed, thus revealing the truth. And truth is often simpler than deception.

Solution 3:

The only term that comes immediately to my mind is "deceptively simple".

As an example, if I ask you to tell me the area of a triangle with sides 4, 7, and 11, you might go and dig up Heron's Formula (area=sqrt(s(s-a)(s-b)(s-c)), where s=(a+b+c)/2) and start calculating it, or you might notice that side a + side b = side c, and thus the "triangle" is actually 2 straight lines, and therefore the area must be 0.