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tutorial_particles_2d.md

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+# Particle Systems (2D)
+
+## Intro
+
+A simple (but flexible enough for most uses) particle system is provided. Particle systems are used to simulate complex physical effects such as sparks, fire, magic particles, smoke, mist, magic, etc. 
+
+The idea is that a "particle" is emitted every a fixed interval and with a fixed lifetime. During his lifetime, every particle will have the same base behavior. What makes every particle different and provides a more organic look is the "randomness" associated to each parameter. In essence, creating a particle system means setting base physics parameters and then adding randomness to them.
+
+
+### Particles2D
+
+Particle systems are added to the scene via the [Particles2D](class_particles2d) node. They are enabled by default and start emitting white points downwards (as affected by the gravity). This provides a reasonable starting point to start adapting it to our needs.
+
+<p align="center"><img src="images/particles1.png"></p>
+
+### Texture
+
+A particle system uses a single texture (in the future this might be extended to animated textures via spritesheet). The texture is set via the relevant texture property:
+
+<p align="center"><img src="images/particles2.png"></p>
+
+## Physics Variables
+
+Before taking a look at the global parameters for the particle system, let's first see what happens when the physics variables are tweaked.
+
+#### Direction
+
+This is the base angle at which particles emit. Default is 0 (down):
+
+<p align="center"><img src="images/paranim1.gif"></p>
+
+Changing it will change the emissor direction, but gravity will still affect them:
+
+<p align="center"><img src="images/paranim2.gif"></p>
+