add some y offset to particle
add some y offset to particle

cdshinde/d3-cookbook,UsabilityEtc/d3-cookbook,aliciajin/d3-cookbook,NickQiZhu/d3-cookbook,krahman/d3-cookbook,congpeixin/d3-cookbook,owen-dall/d3-cookbook,cuilaixi/d3-cookbook,congpeixin/d3-cookbook,pb-pravin/d3-cookbook,caihanling/d3-cookbook,ubergrafik/d3-cookbook,krahman/d3-cookbook,pb-pravin/d3-cookbook,owen-dall/d3-cookbook,pcuci/d3-cookbook,lrmlll/d3-cookbook,caihanling/d3-cookbook,DataVizApril/d3-cookbook,lifun/d3-cookbook,lifun/d3-cookbook,cdshinde/d3-cookbook,congpeixin/d3-cookbook,aruis/d3-cookbook,lrmlll/d3-cookbook,cdshinde/d3-cookbook,krahman/d3-cookbook,cuilaixi/d3-cookbook,caihanling/d3-cookbook,aruis/d3-cookbook,UsabilityEtc/d3-cookbook,UsabilityEtc/d3-cookbook,pb-pravin/d3-cookbook,DataVizApril/d3-cookbook,lrmlll/d3-cookbook,NickQiZhu/d3-cookbook,cuilaixi/d3-cookbook,pcuci/d3-cookbook,pcuci/d3-cookbook,ubergrafik/d3-cookbook,aliciajin/d3-cookbook,lifun/d3-cookbook,owen-dall/d3-cookbook,NickQiZhu/d3-cookbook,aruis/d3-cookbook,ubergrafik/d3-cookbook,DataVizApril/d3-cookbook,aliciajin/d3-cookbook