Splash

--By xXxMoNkEyMaNxXx (Whitemambaa)
local arg={...}

local next=next
local time=os.time
local tick=os.clock

local sqrt=math.sqrt
local ceil=math.ceil

local match=string.match

local remove=table.remove

local pull=os.pullEvent
local setAlarm=os.setAlarm

local paint=term.write
local setBGC=term.setBackgroundColour
local setPos=term.setCursorPos


local speed=8
local length=1.5
local palette={colours.black,colours.grey,colours.lightGrey,colours.white}

local size={term.getSize()}
local maxAge=(sqrt(size[1]*size[1]+size[2]*size[2])+length)/speed
local splashes={}

local function draw(t)
    local radii={}
    for i=1,#splashes do
        radii[i]=(t-splashes[i].t)*speed
    end
    for x=1,size[1] do
        for y=1,size[2] do
            local prod=1
            for i=1,#splashes do
                local s=splashes[i]
                local d=(radii[i]-sqrt((s[1]-x)^2+(s[2]-y)^2))/length
                local dsq=d*d
                if dsq<1 then
                    prod=prod*(1-sqrt(1-dsq))
                end
            end
            setPos(x,y)
            if prod<1 then
                setBGC(palette[ceil(#palette*(1-prod))])
            else
                setBGC(32768)
            end
            paint' '
        end
    end
end

local enabled=true
while enabled do
    local event={pull()}
    local now=tick()
    for i=#splashes,1,-1 do
        if now-splashes[i].t>=maxAge then
            remove(splashes,i)
        end
    end
    if event[1]=="mouse_click" then
        if #splashes==0 then
            setAlarm((time()+0.001)%24)
        end
        splashes[#splashes+1]={event[3],event[4],t=now}
    end
    if #splashes>0 then
        draw(now)
        if event[1]=="alarm" then
            setAlarm((time()+0.001)%24)
        end
    end
end