Asteroid cannon

gistfile1.txt

--# Main
--Asteroid run

INTRO,PLAY,END=1,2,3

function setup()
    displayMode(FULLSCREEN)
    LoadImages() --read in all the images we will use
    CreateSights() --create gunsight image to save us drawing it each time
    Settings() --set up games
    state=INTRO
end

function Settings()    
    --min/max positions of asteroids, and position of ship, on screen
    minX,maxX,minY,maxY,shipX,shipY=-WIDTH/2,WIDTH/2,-HEIGHT/2,HEIGHT/2,0,0
    --all asteroids start from the same distance away
    --you can set how many are created per second
    --alreadyCreated keeps track of how many have been created so far
    startDist,asteroidRate,timer,alreadyCreated,A=100,20,0,0,{}
    laserRange=25 --how far the laser can shoot
    --HitRadius calculates how far from the centre of the screen an asteroid can be before it misses the ship
    local s=startDist^.5 
    HitRadius=vec2(WIDTH/2/s,HEIGHT/2/s)
    warning={s=1} --a tween is used to make dangerous asteroids pulse by changing the ellipse size
    wt=tween(2,warning,{s=6},{easing=tween.easing.linear,loop = tween.loop.pingpong } )
end

function LoadImages()
    Rocks={} for i=1,9 do 
    Rocks[#Rocks+1]=readImage("Tyrian Remastered:Space Ice "..i) end
    for i=1,7 do Rocks[#Rocks+1]=readImage("Tyrian Remastered:Rock "..i) end
end


--start game when screen is touched
function touched(t)
    if t.state==ENDED then Start() end 
end

--start playing
function Start() --triggered by touch on screen
    state=PLAY 
    timer=0
    Shields=100 --health!
end

function AddAsteroid()
    local a={}
    --a.x, a.y = position on screen, a.rs=rotation direction 
    a.x,a.y,a.rs=math.random(minX,maxX),math.random(minY,maxY),math.random(-1,1)
    --a.s=size, a.d=start distance, a.img=sprite
    a.s,a.d,a.r,a.img=math.random(1,3),startDist,0,Rocks[math.random(#Rocks)]
    --if it will hit ship, pre-calculate damage
    if math.abs(a.x)<HitRadius.x and math.abs(a.y)<HitRadius.y then 
        a.h=5*a.s
    end
    table.insert(A,a) --add to table
end

function draw()
    background(0)
    if state==INTRO then DrawIntro()
    elseif state==PLAY then DrawPlay()
    elseif state==END then DrawEnd() end
end

function DrawPlay()
    timer=timer+DeltaTime
    local a=timer*asteroidRate --calculate how many asteroids should have been created so far
    for i=1,a-alreadyCreated do AddAsteroid() end --add any that haven't been created
    alreadyCreated=math.floor(a)
    --set aim using Gravity to measure iPad tilt
    --you can make the aim more or less sensitive by varying sensitivity
    sensitivity=3
    aim=vec2((Gravity.x*sensitivity+1)*WIDTH/2,(Gravity.y*sensitivity+1)*HEIGHT/2)
    sprite(sights,aim.x,aim.y) --draw aiming circle
    --draw asteroids and check if exploded
    local n=0
    fill(255,255,0,50) --warning colour
    for i,a in pairs(A) do
        n,a.d=n+1,a.d-.1  --adjust distance from ship
        if a.d==0 then table.remove(A,i) --delete when they pass the ship
        else 
            a.r=a.r+a.rs --rotate
            --this formula is a rather arbitrary way of figuring out how asteroids spread out as they approach
            local v=(startDist/a.d)^.5
            local xx,yy=WIDTH/2+a.x*v,HEIGHT/2+a.y*v
            --remove asteroids that go off the screen
            if xx<0 or xx>WIDTH or yy<0 or yy>HEIGHT then 
                table.remove(A,i)
            else
                --check if it is very close and hit the ship
                if a.d<1 and a.h then
                    Shields=Shields-a.h
                    sound(SOUND_EXPLODE, 39100+math.random(0,100))
                    table.remove(A,i)
                    if Shields<0 then state=END end
                else 
                    local w=a.img.width*a.s/a.d --visible size of asteroid
                    --check if we have hit it with the laser
                    if a.d<laserRange and vec2(xx,yy):dist(aim)<w then
                        sound(SOUND_SHOOT, 39124)
                        table.remove(A,i)
                    else --draw asteroid
                        if a.h and a.d<laserRange then ellipse(xx,yy,w*warning.s) end
                        if w>3 then
                            pushMatrix()
                            translate(xx,yy)
                            rotate(a.r)
                            sprite(a.img,0,0,w)
                            popMatrix()
                        else sprite(a.img,xx,yy,w) end
                    end
                end
            end
        end
    end 
    pushStyle()
    fill(255,255,0)
    textMode(CORNER)
    text("Shields "..Shields,50,HEIGHT-70)
    text("Time "..math.floor(timer),50,HEIGHT-90)
    popStyle()
    
end

--note DrawTextScreen is used to give consistent look to text screens
--this function only provides the text needed for the intro
function DrawIntro()
    local t="You are passing through a band of asteroids, and the automatic cannon has broken down.\n\n"
    t=t.."You have to destroy all asteroids that may hit the ship, by tilting the iPad until the gunsights are over an asteroid. The gun will shoot automatically if the asteroid is in range.\n\n"
    t=t.."Watch out for the asteroids which pulse in yellow. The ship has tagged these as dangerous.\n\n"
    t=t.."Good luck, and try to survive as long as possible before your shields are destroyed.\n\n"
    DrawTextScreen(t)
end

function DrawEnd()
    local t="You survived for "..math.floor(timer).." seconds."
    DrawTextScreen(t)
end

function DrawTextScreen(txt)
    pushStyle()
    --title
    font("MarkerFelt-Wide")
    fontSize(48)
    fill(255)
    text("Asteroid Run",WIDTH/2,HEIGHT*0.8)
    font("ArialMT")
    textWrapWidth(500)
    fontSize(18)
    text(txt,WIDTH/2,HEIGHT/2)
    fill(255,255,0)
    text("Press the screen to start playing",WIDTH/2,HEIGHT/4)
    popStyle() 
end

--create gunsight image
function CreateSights()
    sights=image(120,120)
    setContext(sights)
    pushStyle()
    stroke(255,255,0,200)
    strokeWidth(1)
    fill(0,0,0,0)
    ellipse(60,60,100)
    ellipse(60,60,50)
    ellipse(60,60,10)
    line(0,60,120,60)
    line(60,0,60,120)
    popStyle()    
    setContext()
end