to snake
setvars
clearscreen
setscreencolor :bgcolour
run pick [
	[maze_1]
;	[maze_2]
]
repeat :foodcount [makefood]
setturtle 2
penup
hideturtle
setturtle 1
hideturtle
settimer 1 1 [losetail ai turn move pixelcheck]
mouseon [startdrive] [] [stopdrive] [] []
end

to revive
; revives a snake which has hit a wall or tail
settimer 1 1 [losetail ai turn move pixelcheck]
end

to pausesnake
cleartimer 1
print [To resume, use revive.]
end

to ksnake
; EXPERIMENTAL!
setvars
clearscreen
run pick [
	[maze_1]
;	[maze_2]
]
repeat :foodcount [makefood]
setturtle 2
penup
hideturtle
setturtle 1
hideturtle
settimer 1 1 [losetail move pixelcheck]
mouseon [startdrive] [] [stopdrive] [] []
keyboardon [kturn]
setfocus [MSWLogo SCREEN]
end

to ai
; Simple AI to follow food

if :ai_mode [
	ai_main :food_points
]
end

to ai_main :foodpoints
make "lastpos last :foodpoints
make "cx first :lastpos
make "cy last :lastpos
make "tx xcor
make "ty ycor
make "x :cx - :tx
make "y :cy - :ty

if :y > 0 [
	make "newangle arctan (:x / :y)
]

if (AND (:y < 0) (:x > 0)) [
	localmake "temp 0-:y
	make "newangle 90+arctan (:temp / :x)
]

if (AND (:y < 0) (:x < 0)) [
	localmake "temp 0-:y
	make "newangle 270+arctan (:temp / :x)
]

if :newangle < 0 [
	make "newangle :newangle + 360
]

if (OR (:newangle > 360) (:newangle = 360)) [
	make "newangle :newangle - 360
]

ifelse (ABS (:newangle - heading)) < 160 [
	setheading :newangle
][
	;ifelse (COUNT butlast :food_points) > 0 [
	;	ai_main butlast :food_points
	;][
		setheading :newangle
	;]
]
end

to maze_1
; Draw a simple box around the field
penup
setpensize [5 5]
setpencolor :wallcolour
setpos [-300 -300]
pendown
repeat 4 [fd 600 rt 90]
penup
setpencolor :snakecolour
setpensize [1 1]
home
pendown
end

to maze_2
local "maze_2
make "maze_2 "maze_2.bmp		; CHANGE THIS!
ifelse (AND ((first (bitloadsize :maze_2)) = 600) ((last (bitloadsize :maze_2)) = 600)) [
	penup
	setpos [-300 -300]
	bitload :maze_2
	setpos [0 0]
	pendown
	print [Maze II loaded.]
][
	print [The map needs to be 600 by 600.]
]
end

to pixelcheck
; Check whether we have hit our tail
if (pixel = :snakecolour) [
	print [You hit your own tail!]
	if NOT :god_mode [cleartimer 1]
	halt
]
; If not yet dead, check whether we have hit a wall
if (pixel = :wallcolour) [
	print [You have hit a wall!]
	if NOT :god_mode [cleartimer 1]
]
; If not yet dead, check whether we are on poison
if (pixel = :poisoncolour) [
	make "score :score - :poisonpenalty
	print (sentence [You got poisoned! Your score:] :score)
	make "size :size - :poisonpenalty
	setpensize (list :explodesize :explodesize)
	setpencolor :bgcolour
	fd 0
	setpencolor :snakecolour
	setpensize [1 1]
	makepoison
]
; Check whether we're standing on food
if (pixel = :foodcolour) [
	make "score :score + :curspd
	print (sentence [You ate the food! Your score:] :score)
	make "size :size + (:tailgrowth*:curspd)
	setpensize (list :explodesize :explodesize)
	penerase
	fd 0
	penpaint
	setpensize [1 1]
	makefood
	makepoison
]
end

to makefood
; Puts food onto the field
setturtle 3
penup
make "lastpos (list ((random :worldsize)-(:worldsize/2)) ((random :worldsize)-(:worldsize/2)))
setpos :lastpos
make "food_points lput :lastpos :food_points
setpensize (list :foodsize :foodsize)
setpencolor :foodcolour
pendown
fd 0
setpencolor :snakecolour
setpensize [1 1]
penup
home
pendown
setturtle 1
end

to makepoison
; Puts poison onto the field
if (RANDOM 100) < :poisonchance [
	setturtle 3
	penup
	make "lastpos (list ((random :worldsize)-(:worldsize/2)) ((random :worldsize)-(:worldsize/2)))
	setpos :lastpos
	setpensize (list :foodsize :foodsize)
	setpencolor :poisoncolour
	pendown
	fd 0
	setpencolor :snakecolour
	setpensize [1 1]
	penup
	home
	pendown
	setturtle 1
]
end

to losetail
if ((count :points) < :size) [
	stop
]
if (AND ((count :points) > :size) ((count :points) > 1)) [
	while [(AND ((count :points) > :size) ((count :points) > 1))] [
		make "diepoint first :points
		setturtle 2
		setpos :diepoint
		setpixel :bgcolour
		setturtle 1
		make "points butfirst :points
	]
]

end

to move
make "tx xcor
make "ty ycor
make "mx first mousepos
make "my last mousepos
make "xdist abs (:mx - :tx)
make "ydist abs (:my - :ty)
make "dist sqrt (:xdist*:xdist + :ydist*:ydist)
if :dist < :curspd [stop]
repeat :curspd [
	fd 1
	make "tx xcor
	make "ty ycor
	make "ax (round (:tx / 1))*1
	make "ay (round (:ty / 1))*1
	make "ax :tx
	make "ay :ty
	setxy :ax :ay
	make "points lput (list :ax :ay) :points
]
end

to startdrive
make "curspd :curspd + :incspd
end

to startrev
make "curspd -:incspd
end

to stopdrive
if (OR (:curspd > :incspd) (:curspd = :incspd)) [make "curspd :curspd - :incspd]
end

to turn
; Normal turning procedure, guided by mouse, not by AI
if :ai_mode [stop]
make "cx first mousepos
make "cy last mousepos
make "tx xcor
make "ty ycor
make "x :cx - :tx
make "y :cy - :ty

if :y > 0 [
	make "newangle arctan (:x / :y)
]

if (AND (:y < 0) (:x > 0)) [
	localmake "temp 0-:y
	make "newangle 90+arctan (:temp / :x)
]

if (AND (:y < 0) (:x < 0)) [
	localmake "temp 0-:y
	make "newangle 270+arctan (:temp / :x)
]

if :newangle < 0 [
	make "newangle :newangle + 360
]

if (OR (:newangle > 360) (:newangle = 360)) [
	make "newangle :newangle - 360
]

setheading :newangle

end

to kturn
make "oldheading heading
if (char keyboardvalue) = "8 [make "newangle 000]
if (char keyboardvalue) = "6 [make "newangle 090]
if (char keyboardvalue) = "2 [make "newangle 180]
if (char keyboardvalue) = "4 [make "newangle 270]
if (abs (:newangle - :oldheading)) = 180 [
	make "newangle :oldheading
]
if namep "newangle [setheading :newangle]
end

to between :number :bound1 :bound2
ifelse (AND (:number > :bound1) (:number < :bound2)) [
	output "true
][
	output "false
]
end

to setvars
Make "curspd 0						; Current speed (begins at 0)
Make "incspd 1						; Speed increment when mouse is clicked
Make "points []						; List of points of the snake, DON'T CHANGE THIS!
Make "food_points []				; List of points of food (used by AI to track food), DON'T CHANGE THIS!
Make "size 10						; (starting) Size of the snake
Make "tailgrowth 10					; Growth of the tail per food bit
Make "fadecount 1					; Speed at which snake tail dies (experimental)
Make "score 0						; Current score (begins at 0)
Make "worldsize 550					; Size of the world (i.e. the boundary for food to disperse)
Make "foodcount 4				; Number of food bits on the field at any one time (not changeable during game)
Make "god_mode "false				; God mode (cannot die whilst in God mode)
Make "foodsize 10					; Size of food bits
Make "poisonchance 99				; Chance of poison being created (out of 100)
Make "poisonpenalty 1				; Penalty when eating poison
Make "explodesize 20				; DIAMETER of "explosion" around food that is eaten (don't make this too big or too small)
Make "snakecolour [255 255 255]		; Snake colour
Make "foodcolour [253 253 253]		; Food colour
Make "poisoncolour [001 001 001]	; Poison colour
Make "wallcolour [128 128 128]		; Death colour
Make "bgcolour [000 000 000]			; Background colour

; NB: None of these colours should be the same!
; If you want, say, all black, try 000, 001, 002, 003

Make "ai_mode "false				; If TRUE, then autopiloting (works best with a lot of food and high explosions)
end