Glad you found the tutorial helpful.
It does give you a start and while its not a full game, it should point you in the right direction.
As for making attack waves, as I said to Tapewormz, it can be as complex or as easy as you want.
You can combine set movement patterns with a random element so that the user can never quite tell how the enemy will move. As a simple example….. If you have an alien that you want to bounce about the screen, a routine like the following will do it for you:
sync on
sync rate 30
color backdrop 0
hide mouse
load image "alienship.bmp",1
x=320:y=240
asx=1:al=6:a2=10:a3=8:ca=160
sprite 1,x,y,1
do
AM=RND(12)
AMP=RND(20)+10
if am=1 then gosub 1
if am=2 then gosub 2
if am=3 then gosub 3
if am=4 then gosub 4
if am=5 then gosub 5
if am=6 then gosub 6
if am=7 then gosub 7
if am=8 then gosub 8
if am>8 then gosub 6
sync
loop
1:
for t=1 to amp
sprite 1,x,y,1
inc x,2:dec y,2
sync
next t
return
2:
for t=1 to amp
sprite 1,x,y,1
inc x,2:dec y,2
sync
next t
return
3:
for t=1 to amp
sprite 1,x,y,1
inc x,2
sync
next t
return
4:
for t=1 to amp
sprite 1,x,y,1
inc x,2:inc y,2
sync
next t
return
5:
for t=1 to amp
sprite 1,x,y,1
inc y,2
sync
next t
return
6:
for t=1 to amp
sprite 1,x,y,1
dec x,2:inc y,2
sync
next t
return
7:
for t=1 to amp
sprite 1,x,y,1
dec x,2
sync
next t
return
8:
for t=1 to amp
sprite 1,x,y,1
dec x,2:dec y,2
sync
next t
return
(Place this program in the same directory as the 2D Shoot Em Up tutorial)
What it does is to pick a direction using AM (1 to 8... 1=45 degrees upleft: 2 =left: 3=45 degrees downleft: 4=down: 5=45 degrees downright: 6= right: 7=45 degrees upright: 8=up).
We weight it so that there is a better chance of the alien moving forward, by making it pick a number from 0 to 12. Then we pick an amount to move in pixels using AMP.
Then we simply check the value of AM and if it is 1 then we jump to a routine that moves the alien 45 degrees up and to the left.
This example is pure random movement.
You can make it better by putting some other constraints in to it. You may want to check if the alien if going off screen (use the X and Y coordinates) and if it is you may want to bounce it back by using a set routine to move the alien in to a specific direction.
There are many many other things you can do to this routine and I have kept it simple and not compacted it so that its easy to alter.
Hope that some of this helps and remember, the best way to find out how to do something is to mess, mess and then mess some more.
