Rules

Yags is a free and open game system, and anyone is allowed to modify and redistribute their own versions of the game. People are also encouraged to make suggestions for changes and additions to the rules, or even submit their own additional modules.

It is important to note however that though Yags has been written over many years, and has stolen ideas from countless other games, it does have an overall aim. Going too far beyond what Yags was designed to achieve is probably more trouble than its worth, and you're better off designing your own system from scratch (or starting with another system as a base).

Crunchiness

In RPG terms, a crunchy rule system is one where the rules themselves are interesting. Interesting doesn't mean good of course, and some people don't like a system to be crunchy. If you believe that the rules should be as light as possible, and keep out of the way of the telling of the story, then Yags is probably not for you (Fringe is another Free game which might be more up your street).

Crunch can be in the form of complex rules, but it can also be in options available (such as lots of skills or character abilities).

GURPS is a good example of a very crunchy system - there is a wide range of options for character generation, and the rules are long and complex, covering most conceivable scenarios. Yags is not as crunchy as this however.

Over The Edge is an example of a very crunch-light game system, where it's difficult to spend more than a couple of minutes designing a character. Yags is more crunchy than this.

It should be noted that despite this, Yags aims to be as simple as possible - but no simpler. Rules are added where it is considered interesting to flesh out things in more detail, and simplified in other places where they don't add anything to the game.

This web site details some of the crunchier aspects of Yags, and gives some reasoning behind the rules.

Cinematic Realism

Yags aims for Cinematic Realism. Though this sounds like a self-contradictory statement, it means that there is an aim to keep the core rules grounded in low fantasy realism, whilst allowing PCs to still be heroes through training and experience (note that this may differ from artistic meanings of the term). You can be awesome, but you can't be a super hero.

How much the cinematic aspects are cranked up are down to the GM and the type of characters she allows. A highly skilled special forces operative could take out lots of mooks by careful use of cover, tactics and accurate controlled shots. However, a single mook that has crept up from behind can still take the operative out with a single well placed shot.

Working together as a team, a highly skilled group of PCs can be devastating to less well trained 'normals' - just as in real life.

The type of cinema that Yags tries to duplicate then (at least, from the action perspective) is the tale of the bloodied hero who wins out through skill and determination, but can never allow themselves to get complacement. Heroes such as Conan, Beatrice Kiddo or John McClane.