Well, the speed without optimizations was already adapted to the game. I tried the optimizations like one table instead of two for X and Y, but I couldn't see the speed changing. I think that the difference exist, but it's too small.
I will post the final version in a few hours including a first page which contains explanations (keys, etc)

I updated the first post with a playable version, screenies, and a link to the .tns (unfortunately the website where I uploaded it has a lot of ads)
This may be the final version, because the game is finished and the gameplay seems good for me.
Some optimizations still can be done, but the speed is fast enough. (If you think that it's too slow, try to reach 100 points )

EDIT : I just saw we could attach files No more ads, now.

I looked through some of your code, and I noticed a few things wrong with it:

- unoptimized math commands.  While it's not huge, using player+=10 is a lot better than player=player+10.
- what's the deal with all of the for loops?  I don't see the point in many of them.
- you should chain if statements together more, it'll remove the need for much of the redundancies and might even half your code size.
- why do you assign different functions to keys instead of just making a checkKeys() function or just putting all checks inline?  Or are you overriding previously existing functions provided by an NLua module?

I just started in LUA...
The '+=' works ? Omg I was fed up with all the 'player=player+10'
I will check all the other things tomorrow...

Hello everybody !

That's my first post here, so I'll try to introduce myself.
First, I'm French. I am a very bad English speaker (well, I'm fifteen and our English teacher sucks) so I apologize for all the nonsenses and mistakes that I'll do.
I was a member of TI-Bank, and I left this website because of all the troubles (fights between admins, etc)
So the most interesting website about calculators was Omnimaga, and I registered.
I have a TI-83+ and a TI-Nspire (Non-CAS & clickpad), and I code in Axe, in C for Nspire and in Lua. I also program in C with OpenGL on my PC, but that's not really interesting.
Well, I think I've enough talked about myself.

I made this post because I wanted feedbacks (not sure about this word) for my newest project, a Space Invaders game in Lua.
It looks like the original game, excepted that there's only one kind of enemies, and there's no "houses". Also, the enemies doesn't go faster as they go down, but the speed increases with the level.

The player can shoot with the up arrow, but that's not really convenient. If you had any better idea...
Also, I've never tried it on a calc. I don't have any CX and I use the OS 2.0.1 on my clickpad. If you could try it on your calc (and post your hi-score !)
EDIT : final version, updated.

Thank you,
Chockosta (Loic Pujet)

Lua code (Edited, final version):
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("Lives:"..tostring(lives).." Score:"..tostring(score).." Level:"..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 var.recall("highscore")==nil then
var.store("highscore",0)
else
if var.recall("highscore")<score then
var.store("highscore",score)
document.markChanged()
end
end
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).."        High score : "..tostring(var.recall("highscore")),50,50, "top")
if not originalColors then gc:setColorRGB(0,0,255) end
if locale.name()=="fr" then
gc:drawString("Appuyez sur R pour rejouer",50,150,"top")
else
gc:drawString("Press R to try again",80,150,"top")
end
end

if wait>0.01 then
timer.start(wait)
else
timer.start(0.01)
end

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]>295 then
down="yes"
end
end
else
for i=1,21,1 do
if aliensX[i]<5 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()
end
I attached the .tns It works on OS 3.0.1 and OS 3.0.2 (edited : bug fixed)