' Bobsleigh 1.1
' Allan Crossman, 2001

' Inspired by but not copied from "The Dragon 32 Book of Games"

' Move with 4 and 6.
' Keep the sleigh in the course!

hide console
hidecursor
fullscreen mode screen width, screen height, 8

randomize timer

width = 300
depth = 400

left = screen width / 2 - (width / 2)
top = screen height / 2 - (depth / 2)
right = screen width / 2 + (width / 2)
bottom = screen height / 2 + (depth / 2)

disable done

dim left(depth)
dim right(depth)

slopeleft = 1
sloperight = 2

startseparation = 60      ' Higher is easier
minseparation = 30        ' How close the two sides can come to each other
verticalpos = 40

decreasetime = 2000       ' ie every 2000 ticks it reduces the width
decreasevalue = 2         ' How much each side closes in

changeprob = 0.025

backcolor 0, 0, 0
forecolor 65535, 65535, 65535

virtue = init screen(0, 0, width, depth)

Restart:
set screen to virtue
cls

mypos = width / 2
separation = startseparation

forecolor 65535, 65535, 65535

x = 0
y = -1
makestart:
x = x + 1
y = y + 1
left(y) = x
right(y) = width - x
if right(y) - left(y) > separation then goto makestart
makerest:
y = y + 1
if y < depth then
   left(y) = x
   right(y) = width - x
   goto makerest
end if

for y = 0 to depth
   plot left(y), y
   plot right(y), y
next y

copyrect 0, 0, width, depth, left, top, right, bottom, 0, virtue, 0

if rnd < 0.5 then slopedirection = slopeleft else slopedirection = sloperight

tick = 0

set screen to console
cls
set screen to virtue

mainloop:

tick = tick + 1

set screen to console
textmode 0
forecolor 0, 65535, 0
text left, top - 30, "Score: " + str$(tick)
text right - 100, top - 30, "High: " + str$(highscore)
set screen to virtue

starttime = timer

keymap scan
if keymap key ("q") then
   goto EndProg
end if
if keymap key ("4") then
   mypos = mypos - 1
end if
if keymap key ("6") then
   mypos = mypos + 1
end if

if mypos < left(verticalpos) or mypos > right(verticalpos) then
   if tick > highscore then highscore = tick
   wait 1
   goto Restart
end if

for y = 0 to depth - 2
   left(y) = left(y + 1)
   right(y) = right(y + 1)
next y

if tick mod decreasetime = 0 then decreaseflag = 1

if decreaseflag then
   if decreased = decreasevalue or separation - 2 < minseparation then
      decreaseflag = 0
      decreased = 0
   else
      left(depth - 1) = left(depth - 2) + 1
      right(depth - 1) = right(depth - 2) - 1
      separation = separation - 2
      decreased = decreased + 1
   end if
end if

if decreaseflag = 0 then   ' otherwise the generation has already been done
   if slopedirection = slopeleft then
      if left(depth - 1) < 20 then
         slopedirection = sloperight
         left(depth - 1) = 20
      else
         left(depth - 1) = left(depth - 2) - 1
      end if
      right(depth - 1) = left(depth - 1) + separation
   else
      if right(depth - 1) > width - 20 then
         slopedirection = slopeleft
         right(depth - 1) = width - 20
      else
         right(depth - 1) = right(depth - 2) + 1
      end if
      left(depth - 1) = right(depth - 1) - separation
   end if
end if

if rnd < changeprob then
   if slopedirection = slopeleft then slopedirection = sloperight else slopedirection = slopeleft
end if

copyrect 0, 1, width, depth, 0, 0, width, depth - 1, 0, virtue, virtue
forecolor 0, 0, 0
line 0, depth - 1, width, depth - 1
forecolor 65535, 65535, 65535
plot left(depth - 1), depth - 1
plot right(depth - 1), depth - 1

for y = verticalpos - 7 to verticalpos
   plot left(y), y
   plot right(y), y
next y

forecolor 65535, 65535, 0
fcircle mypos, verticalpos, 5
copyrect 0, 0, width, depth, left, top, right, bottom, 0, virtue, console
forecolor 0, 0, 0
fcircle mypos, verticalpos, 5

KillTime:
if abs(timer - starttime) < 0.005 then goto KillTime

goto mainloop

EndProg:
wait 1
set screen to console
kill screen virtue
normal screen
showcursor
end