Okay, I think my game is finished. I attach the last release.
Please test this, and post here if you find any bug or problem. (By the way, the 3 shots to destroy a block are increased, now it's 5 shots)

EDIT : I removed the attachment. If you're looking for the game, see below.

Sure !
Here it is :
function on.charIn(ch)
if ch=="r" then
blocks={5,5,5,5,5,5,5,5,5,5,5,5}
blockAttacked=0
game="notfinished"
score=0
player=100
shotX=0
shotY=0
level=1
wait=0.04
aliensDir="right"
down="no"
aliensX={}
aliensY={}
shotsX={}
shotsY={}
lives=3
for i=1,21,1 do
aliensX[i]=(i-1)%7*31+1
aliensY[i]=math.floor((i-1)/7)*25+10
shotsX[i]=aliensX[i]
shotsY[i]=200
end
end
if ch=="c" then
originalColors=not originalColors
end
end

function blocktest(x,y)
blockAttacked=0
if y>170 and y<177 then
if x>30 and x<40 and blocks[1]>0 then
blockAttacked=1
elseif x>40 and x<=50 and blocks[2]>0 then
blockAttacked=2
elseif x>50 and x<=60 and blocks[3]>0 then
blockAttacked=3
elseif x>60 and x<=70 and blocks[4]>0 then
blockAttacked=4
elseif x>140 and x<=150 and blocks[5]>0 then
blockAttacked=5
elseif x>150 and x<=160 and blocks[6]>0 then
blockAttacked=6
elseif x>160 and x<=170 and blocks[7]>0 then
blockAttacked=7
elseif x>170 and x<=180 and blocks[8]>0 then
blockAttacked=8
elseif x>250 and x<=260 and blocks[9]>0 then
blockAttacked=9
elseif x>260 and x<=270 and blocks[10]>0 then
blockAttacked=10
elseif x>270 and x<=280 and blocks[11]>0 then
blockAttacked=11
elseif x>280 and x<=290 and blocks[12]>0 then
blockAttacked=12
end
end
end


on.charIn("r")


function on.arrowLeft()
if player>0 then
player=player-10
end
end
function on.arrowRight()
if player<290 then
player=player+10
end
end
function on.tabKey()
if shotY<=0 then
shotY=195
shotX=player+13
end
end


function on.paint(gc)
if originalColors then
gc:setColorRGB(0,0,0)
gc:fillRect(0,0,platform.window:width(),platform.window:height())
end

if not originalColors then gc:setColorRGB(0,0,0)
else gc:setColorRGB(255,255,255) end
gc:setPen("thin","smooth")
gc:setFont("sansserif","r",8)
gc:drawString("Lua Alien Invaders - Par Loic Pujet",10,200,"top")

if game=="notfinished" then
if not originalColors then gc:setColorRGB(200,0,0)
else gc:setColorRGB(255,255,255) end
for i=1,21,1 do
if aliensY[i]~=0 then
gc:drawArc(aliensX[i]+4,aliensY[i]-9,10,10,0,360)
gc:fillArc(aliensX[i]-5,aliensY[i]-4,28,8,0,360)
end
end

if not originalColors then gc:setColorRGB(0,0,200)
else gc:setColorRGB(255,255,0) end
for i=1,21,1 do
if shotsY[i]<200 then
gc:fillRect(shotsX[i],shotsY[i],2,5)
end
end
if shotY>0 then
gc:fillRect(shotX,shotY,4,6)
end

if not originalColors then gc:setColorRGB(100,0,255)
else gc:setColorRGB(0,255,0) end
gc:fillRect(player,195,30,10)
gc:fillRect(player+13,191,4,4)
gc:setFont("sansserif","r",10)
gc:drawString("Vies:"..tostring(lives).." Score:"..tostring(score).." Niveau:"..tostring(level),0,0,"top")

if not originalColors then add=3
else add=0 end
for i=1,12,1 do
if blocks[i]>0 then
gc:fillRect(i*10+math.floor((i-1)/4)*70+20,180-blocks[i]*2,10,blocks[i]*2)
end
end
else
if not originalColors then gc:setColorRGB(0,0,0)
else gc:setColorRGB(255,255,255) end
gc:setFont("sansserif","b",15)
gc:drawString("Score : "..tostring(score),100,50, "top")
if not originalColors then gc:setColorRGB(0,0,255) end
gc:drawString("Appuyez sur R pour rejouer",50,150,"top")
end

timer.start(wait)
end


function on.timer()
timer.stop()

if game=="notfinished" then
if aliensDir=="right" then
for i=1,21,1 do
if aliensY[i]>0 then
aliensX[i]=aliensX[i]+1
end
end
else
for i=1,21,1 do
if aliensY[i]>0 then
aliensX[i]=aliensX[i]-1
end
end
end

if aliensDir=="right" then
for i=1,21,1 do
if aliensX[i]>305 then
down="yes"
end
end
else
for i=1,21,1 do
if aliensX[i]<15 then
down="yes"
end
end
end

if down=="yes" then
down="no"
for i=1,21,1 do
if aliensY[i]>0 then
aliensY[i]=aliensY[i]+25
end
end
if aliensDir=="left" then
aliensDir="right"
else
aliensDir="left"
end
end

for i=1,21,1 do
if aliensY[i]>180 then
game="finished"
end

if shotsY[i]>=200 and aliensY[i]~=0 then
if math.random(1,100)==5 then
shotsY[i]=aliensY[i]+math.random(1,10)
shotsX[i]=aliensX[i]
end
else
shotsY[i]=shotsY[i]+3
end

blocktest(shotsX[i],shotsY[i])
if blockAttacked>0 then
shotsY[i]=201
blocks[blockAttacked]=blocks[blockAttacked]-1
end

if shotsY[i]<200 then
if shotsY[i]>195 and shotsX[i]>player and shotsX[i]<player+30 then
lives=lives-1
shotsY[i]=200
end
end

if shotY>0 and shotY>aliensY[i]-5 and shotY<aliensY[i]+5 and shotX>aliensX[i]-10 and shotX<aliensX[i]+21 then
aliensY[i]=0
aliensX[i]=100
shotY=0
score=score+1
end
end

blocktest(shotX,shotY)
if blockAttacked>0 then
shotY=-1
blocks[blockAttacked]=blocks[blockAttacked]-1
end

if shotY>=0 then
shotY=shotY-5
end

if lives<=0 then
game="finished"
end


wintest=0
for i=1,21,1 do
wintest=wintest+aliensY[i]
end

if wintest==0 then
if wait>0.01 then
wait=wait-0.005
end
level=level+1
aliensDir="right"
down="no"
for i=1,21,1 do
aliensX[i]=(i-1)%7*31+1
aliensY[i]=math.floor((i-1)/7)*25+10
shotsX[i]=aliensX[i]
shotsY[i]=200
end
end
end

platform.window:invalidate()
endI think that my code is pretty awful, good luck when reading it
(I know, I should add comments)

Nice, someone with a CX should make a video

Also guys if you use an emu or an actual CX, don't keep mashing the C key non stop (seizure, much? )

Bug fixed ! If you went to the level 7, there was an error message.
For the ones who still care of my game, I attach it to this post. (And to the first post)
It's the fourth "final version" of my space invaders  

Yes, so the French becomes a bit useless, because a lot of French people (including me) have their calc in English.
And yes, English is the default language.

Er... I think so.
(I mean their calc language is English, not that they use their calc in English class )

Little modification, quite useless...
When the var "highscore" doesn't exist, it is created. It can be useful if you delete this var (strange, but why not ?) or if you open the scratchpad (strange too...)

So you can download it, but if you already have the last version, it's useless.

PS : I also edited the first post.