-- Axis are from 0 to 1
-- Axis(x, y, c, r) - axis variable
-- {,} - axis texture [1]: texture y position [2]: texture length
function make_particle(_x, _y, _c, _r, _maxl)
 p = {
 x=_x,
 y=_y,
 c=_c,
 r=_r,
 l=0,
 maxl=_maxl
 }
 add(particles, p)
 return p
end
function axis(_n, _v, _a, _i)
 return {
  n=_n or 0,
  v=_v or 0,
  a=_a or 0,
  i=_i or 1
 }
end
function update_particle(p)
 -- Update all axis
 local _l = p.l / p.maxl
 _r = get_axis(p.r, _l)
 update_axis(p.x, cos(_r), -p.y.v * sin(_r))
 update_axis(p.y, cos(_r), p.x.v * sin(_r))
 update_axis(p.c)
 update_axis(p.r)
 if(p.l >= p.maxl) del(particles, p)
 p.l += 1
end
function draw_particle(p)
 local _l = p.l / p.maxl
 pset(flr(get_axis(p.x, _l) * 127 + 0.5), flr(get_axis(p.y, _l) * 127 + 0.5), flr(get_axis(p.c, _l) * 15 + 0.5))
end
function make_emitter(_f, _l, _r)
 add(emitters, {f=_f, l=_l, r=_r or 1})
end
function update_emitter(e)
 if(e.l % e.r == 0) e.f()
 e.l -= 1
 if(e.l<=0) del(emitters, e)
end

function update_axis(a, m, o)
 if not is_texture_axis(a) then
  a.v += a.a -- Add acceleration
  a.n += a.v * (m or 1) + (o or 0) -- Add velocity
  a.v *= a.i -- Modify by inertia
 end
end
function get_axis(a, l)
 if is_texture_axis(a) then
  return sget(flr(l * (a[2]-0.001)), a[1]) / 15 -- Get value at addr
 else 
  return a.n
 end
end
function is_texture_axis(a)
 return a.n == nil
end