Q:

Representing Wind in a Block-Based Game

I'm creating a game inside of a game called "ROBLOX".   The game gives you some scripting tools to allow me to basically create anything I want.   The world is created up by decently large blocks.   There are few exceptions to this (such as ramps, spheres, tubes, etc.) 
I want to create a subtle hint of wind.   It will be affecting the game play a little bit and I want the wind to be predictable.   I first thought of creating a flag, but, a flag isn't very well made in such a game as ROBLOX. 
So my question is, what different kinds of way can I imply that there is wind?   What other methods will provide me with a natural representation of wind (I don’t want to put a meter or something, I want them to have to find it/figure it out for themselves). 

A:

Often games will use semi-transparent blocks with that good old 'wisp' effect that gives the impression of wind.  A kind of white swirl in the direction the wind is, I'll try to find a sprite sheet to show you what I mean later. 
Here is a screenshot of a tile-based game some friends of mine made, you can see the wind represented by the white 'swirls' and it tiled pretty well. 
http://www.thomas-planques.com/wp-content/uploads/Level%20Design%205%20-%20Jump%20Gap.jpg
Here there are some prite sheets for special effects; the wind one looks more like a tornado, a bit of clever editing and transparency may help it 'calm down'. 
As Olhovsky said, you could also use particles, this is really dependant on what type of 'feel' you want your game to have, you could mix particles with animated floor tiles (moving grass for example). 

A:

Draw small transparent particles that move in the direction of the wind. 
Like snow particles, except they could just be (very) small grey puffs.  Apply a combination of sin functions to the particle positions to offset them from their usual path, to make them swirve around a bit (e.g. move upward sometimes), so that they don't always simply fall in one direction (which would make them look like rain/snow instead). 
If you want to maintain a blocky look, just make the particles small transparent squares (or cubes). 

A:

SFX can strongly improve the illusion of wind, especially when used in conjunction with a subtle visual effect.   
You can even use the volume of the sound in comparison with the background sounds/music to imply strength of wind.   (You don't necessarily have to keep raising the volume of the wind for this, having the background sounds/music fade slightly as you reach more intense wind can have just as much if not more of an effect without simultaneously making your game too loud)

