Cave Navigator by loudscotsbloke

The Competition Rules: Write a game in no more than 10 lines of code, with
no more than 80* characters per line. Using only the standard power on built-in
language.

My System of Choice: Mattel Electronics Aquarius
Programmer: Roy Templeman
Language: BASIC v1.0

*The Aquarius only supports 72 characters per line!

CAVE NAVIGATOR – Source Code
0?chr$(11):s=0:w=13:l=12348:r=l+880:q=.5:fora=0to19:?:next:?"GO!"
1poker,246:poker+w,246:s=s+1:ifrnd(1)>qandr>13225thenr=r-1:z=z+1:b=4
2ifrnd(1)>qandr<13235-dthenr=r+1:k$=inkey$
3ifk{{ APP_CONTENT }}lt;>"z"andk{{ APP_CONTENT }}lt;>"x"then5:dataC,A,V,E," ",N,A,V,I,G,A,T,O,R," ",2,1
4y=l:a$=k$:u=int(w*rnd(1)+1):poker+u,79:ifk=79thensound(500,10):s=s+50
5y=l:ifa$="z"andy>12329theny=y-1:pokey-1,7
6ifa$="x"andy<12367theny=y+1:pokey+1,6:z=0
7ifpeek(y+40)=246orz>20orr-l>883orr-l<865thensound(20,800):goto9
8?:pokey,25:pokey+1024,22:l=y:w=w-0.02:k=peek(y+80):goto1
9poke(y+80),209:?:?"Dead! You Scored:";s:fori=0to4000:next:a$="":run

Game Rules and Instructions
You have been sent to an alien planet
to investigate the rich deposits of ‘O’,
a vital energy source for the planetary
defence system. The deposits are
deep beneath the surface, trapped
within caves that descend in to the
alien planets core. You must navigate
your shuttle pod using the ‘z’ and ‘x’
keys, this will activate the pods side
thrusters and move you from side to
side, but once on the move the shuttle
will continue to move in that direction!
You must avoid hitting the cave walls,
while trying to navigate on to the ‘O’
deposits. This is harder than it seems
however, as the magnetic properties
of the walls are playing havoc with the
shuttles thrusters! Trying to navigate
on to the vital ‘O’ deposits is
extremely difficult as you must be
precise in order to get the vital energy.
If you successfully manage to grab the ‘O’ you will hear a confirmation beep, but you
must stay alert! Successfully grabbing some ‘O’ will increase your score by 50 points!
So it is well worth pursuing. Hitting the walls will result in instant death! And the game
will start again. Be warned though.. the cave walls get narrower every 100 points and
the amount of ‘O’ depletes the deeper you go. Try to stay alive for as long as possible
and collect as much ‘O’ energy as you can on your way down! Carry on commander!
And good luck!