If it could help you to understand :

Hmm, it actually seems as though they DO have 5.1.4 on it O.o  No idea why the += operators aren't working then.  I explicitly remember being able to use them when I used Lua a few years ago, and I've seen code examples with double ops in them.

Hmm, it actually seems as though they DO have 5.1.4 on it O.o  No idea why the += operators aren't working then.  I explicitly remember being able to use them when I used Lua a few years ago, and I've seen code examples with double ops in them.

Well, in the official Manual, " += " appears only one time, in the C integration part :
http://www.lua.org/manual/5.1/manual.html#lua_CFunction

Thanks for your helping, Ashbad. 

For the '+=' operators, I was thinking that I've already tried it.
But I don't really understand the :
for i=1,21,2 do
aliensXY[i]=(math.ceil(i/2)-1)%7*31+1
aliensXY[i+1]=math.floor((math.ceil(i+1/2)-1)/7)*25+10
shotsXY[i]=aliensX[i]
shotsXY[i+1]=200
endWasn't it supposed to be :
for i=1,21,2 do
aliensXY[i]=(math.ceil(i/2)-1)%7*31+1
aliensXY[i+21]=math.floor((math.ceil(i+1/2)-1)/7)*25+10javascript:void(0);
shotsXY[i]=aliensXY[i]
shotsXY[i+21]=200
endAnd all your "aliensXY[i+1]" shouldn't be changed in "aliensXY[i+21]" ? Because there are 21 aliens, and the table should content first their X position, and after their Y pos.

- using numbers for directions rather than strings.

Is it really faster ? I think that it will not really increase the speed...

PS:Well, it is 9:20 in France, but in USA, it may be very early... I will not get any answers until a few hours, I think   

PS:Well, it is 9:20 in France, but in USA, it may be very early... I will not get any answers until a few hours, I think   

Yup, France is about 6-9 hours ahead of the US, so a lot of activity will happen at night in the US, when you're sleeping,and some of your activity will happen when most people in the US are sleeping.  That being said, we do have a few other members from Europe.
Welcome to Omnimaga, Chockosta.  This project looks great.

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.

Good job! Congratulations!