Json:block:particle

The firepit is a good example of how to use those particles ...

	particlePropertiesByType: {
		"firepit-extinct": [
			{
				hsvaColor: [{ avg: 0, var: 0 }, { avg: 0, var: 0 }, { avg: 70, var: 30 },  { avg: 220, var: 50 }],
				opacityEvolve: { transform: "quadratic", factor: -16 },
				gravityEffect: { avg: 0, var: 0 },
				posOffset: [ { avg: 0, var: 0.2 }, { avg: -0.4, var: 0 }, { avg: 0, var: 0.2 }],
				velocity: [ { avg: 0, var: 0.05 }, { avg: 0.1, var: 0.05 }, { avg: 0, var: 0.05 }],
				quantity: { avg: 0.02 },
				size: { avg: 0.3, var: 0.05 },
				sizeEvolve: { transform: "linear", factor: 1.5 },
				particleModel: "Quad"
			}
		],
		"firepit-lit": [
			{
				hsvaColor: [{ avg: 30, var: 20 }, { avg: 255, var: 50 }, { avg: 255, var: 50 },  { avg: 255, var: 0 }],
				gravityEffect: { avg: 0, var: 0 },
				posOffset: [ { avg: 0, var: 0.2 }, { avg: -0.4, var: 0 }, { avg: 0, var: 0.2 }],
				velocity: [ { avg: 0.0, var: 0.05 }, { avg: 0.5, var: 0.1 }, { avg: 0, var: 0.05 }],
				quantity: { avg: 0.1 },
				size: { avg: 0.25, var: 0 },
				glowLevel: 64,
				sizeEvolve: { transform: "quadratic", factor: -0.5 },
				selfPropelled: true
			},
			{
				hsvaColor: [{ avg: 0, var: 0 }, { avg: 0, var: 0 }, { avg: 70, var: 30 },  { avg: 220, var: 50 }],
				opacityEvolve: { transform: "linear", factor: -255 },
				gravityEffect: { avg: 0, var: 0 },
				posOffset: [ { avg: 0, var: 0.2 }, { avg: -0.4, var: 0 }, { avg: 0, var: 0.2 }],
				velocity: [ { avg: 0, var: 0.05 }, { avg: 0.1, var: 0.05 }, { avg: 0, var: 0.05 }],
				quantity: { avg: 0.12 },
				size: { avg: 0.3, var: 0.05 },
				sizeEvolve: { transform: "linear", factor: 1.5 },
				particleModel: "Quad",
				lifeLength: { avg: 5 } 
			}
		]
	},

There is also a complete tutorial about particles.