The simple idea behind the Square Meter Rule is the design and construction of the fastest hull for a given sail area.
The original rule measured the spar length to determine the sail area and had no penalties for sail overlap. This left the design arena open for innovation, and created some of the most advanced sailboats in the world in pre-WWII times. It also attracted the attention of the leading designers. Certainly Swedish, Danish and Norwegian designers were well represented, but also designers from USA, Great Britain, Germany, - names every sailboat-interested around the world holds holy.
The rule also is home to surprisingly many so-called modern sailing gizmos. Many ideas thought to be recent developments were first seen on Square Meters, some even dating back to the early '30s.