Death Valley

Here is the first game from Usborne's Computer Space Games - Death Valley, a simple game in which the player must move left or right (using the cursor keys) in an attempt to avoid the walls of the valley.

      rem death valley
      rem Daniel Isaaman and Jenny Tyler
      rem translated to BB4Win by T Street
      rem 14/03/2013

      mode 10 : off
      print "DEATH VALLEY"
      delay% = 30    : rem how long to wait for the player to press a key
      dead% = false  : rem keeps track of whether you have crashed or not
      go% = 200      : rem number of turns left
      screenWidth% = 70 : rem width of whole screen
      w% = 10        : rem width of valley
      l% = 10        : rem width of left-hand side
      y% = w%        : rem width of middle region
      r% = w%        : rem width of right hand side
        remprint tab(0,0)l%,y%,r%
        rem change the wall positions
        rem randomly move one place left, right or not at all
          d% = rnd(3)-2 : rem sets a random direction -1,0 or +1
          rem check that the new position is not off the screen
        until l%+d%>0 and r%+d%<screenWidth%
        rem change the value of the wall positions depending on the
        rem value of d%
        l% = l% + d%
        r% = r% + d%
        y% = y% - d%
        rem check whether the player is dead
        if l% = 0 or r% = 0 or y% <= 0 then
          dead% = true
        if notdead% then
          rem print walls
          print string$(l%," ")"I";
          print string$(y%," ")"*";
          print string$(r%," ")"I ";
          print string$(y%+l%," ")"RIP"
        if notdead% then
          rem get user input
          time = 0
          g% = inkey(delay%)    : rem wait user to press left or right
          wait( delay% - time ) : rem wait for the rest of the delay time
          rem move the player based on their current movement choice
          case g% of
            when 136 rem left
              y% = y% - 1
              r% = r% + 1
            when 137 rem right
              y% = y% + 1
              r% = r% - 1
          rem reduce number of gos left
          go% = go% - 1
      until go%=0 or dead%
      print"GAME OVER"
      if notdead% then
        print "CONGRATULATIONS!"
        print"You made it!"
        print "Oh, dear!"

How can you change the width of the canyon?
How can you increase the length of the canyon?
There is plenty of scope here for modifications.  How about changing the colours, or redesigning graphics characters?

Death Valley - avoid the walls, or face a nasty end (sort of)!