Gravitation is a natural phenomenon by which objects with mass attract one another.
So two objects A and C with mass that happen to be in, say, a horizontal plane, attract one another. Quite basic actually.
Of course, there are many other objects, C, D ... etc, around so they also attract A and C. Plenty of attractive gravity forces around!
Back to Topic - The Heiwa Challenge.
Upper structural part C consists of many elements with masses and they are dropped ... in the vertical plane in this case.
There is a big mass below, the Earth, and it attracts the part C masses. Evidently the part C masses also attracts the Earth but, let's ignore that effect in the Challenge.
So forces act on the part C masses, that accelerate the C masses.
However, there is this part A in the way of part C on its way to Earth. A has 10 times the total masses of C and is in fact resting on Earth. A also consists of many masses in the form of structural elements of similar type to C.
So C collides with A. What happens? To keep it simple, it is only one little element (mass) of C, lets call it C1, that contacts another little element (mass) of A, let's call it A1 at beginning of collision. The other masses of C and A do not collide with anything, but as all C masses are one way or another connected to C1, they will be affected. Same in A.
The purpose of The Heiwa Challenge is to find out what happens to C1 and the other C masses and to A1 and the other A masses.
Some people believe (there is no evidence) that little C1 and the other C masses some way or another can one-way crush down A1 and all the other A masses. They believe this as somebody has (dis)informed them so. They have not checked the info provided to them! This happens often - you can say there is an info war.
Little C1 and the other C masses are, on the other hand, held together - connected - in various ways and these connections may break when forces/energy are acting upon them in, e.g. a collision. When the C connections are broken, part C is in principle destroyed. Its many masses are disconnected from one another and cannot do much harm when attracted by Earth.
Same for A.
One reason why part C cannot one-way crush down part A is that the connections in part C fail before the connections in part A and/or part C runs out of energy before breaking all its connections. Many people do not believe that basic fact. They are the losers in the info war.
So that's the reason for The Heiwa Challenge. Build any structure where structural part C one-way crushes a similar structural part A (mass A > mass 10C and much more connections in A than C, of course).
You will learn a lot, e.g. that part C cannot one-way crush down part A assisted by gravity only.