Snake with FunSharp

#r "../src/bin/Debug/FunSharp.Library.dll"

open Library

let size = 8.0
let w,h = 80.,60.
GraphicsWindow.Width <- int (size * w)
GraphicsWindow.Height <- int (size * h)
let directions = [(1.,0.);(0.,1.);(-1.,0.);(0.,-1.)]
let opposite dir = (dir + 2) % 4

let position shape =
    (Shapes.GetLeft(shape), Shapes.GetTop(shape))

let create_snake dir =
    let x,y = 30.,30.
    let (dx,dy) = directions.[opposite dir]
    let snake = ResizeArray()
    for i = 0 to 3 do
        let segment = Shapes.AddRectangle(size,size)
        Shapes.Move(segment, size*(x+dx*float i), size*(y+dy*float i))
        snake.Add(segment)
    snake

let move (snake:ResizeArray<_>) (dx,dy) =
    let length = Seq.length snake
    let last = snake.[length-1]
    let first = snake.[0]
    let x = Shapes.GetLeft(first)
    let y = Shapes.GetTop(first)
    for i = length - 1 downto 1 do
        snake.[i] <- snake.[i-1]
    Shapes.Move(last, x+size*dx, y+size*dy)
    snake.[0] <- last

let self_harm (snake:ResizeArray<_>) =
    let (x,y) = position(snake.[0])
    let mutable collided = false
    for i = 1 to snake.Count - 1 do
        let (x',y') = position(snake.[i])
        if x = x' && y = y' then
            collided <- true
    collided

let hit_wall (snake:ResizeArray<_>) =
    let (x,y) = position(snake.[0])
    x <= 0.0 || y <= 0.0 || x >= w*size || y >= h*size

let mutable dir = 0
GraphicsWindow.KeyDown <- fun () ->
    let key = GraphicsWindow.LastKey
    if key = "Right" then dir <- 0
    elif key = "Down" then dir <- 1
    elif key = "Left" then dir <- 2
    elif key = "Up" then dir <- 3

GraphicsWindow.FontSize <- 32.0
while true do
    let prompt = Shapes.AddText("Click to Start")
    Shapes.Move(prompt, 100, 200)
    while not Mouse.IsLeftButtonDown do ()
    Shapes.Remove(prompt)
    let snake = create_snake dir
    let mutable spawn_count = 10
    let apple = Shapes.AddEllipse(size,size)
    Shapes.Move(apple, -size,-size)
    while not (self_harm snake || hit_wall snake) do
        Program.Delay(300)
        move snake (directions.[dir])
        if spawn_count > 0 then
            spawn_count <- spawn_count - 1
            if spawn_count = 0 then
                Shapes.Move(apple, float(Math.GetRandomNumber(int(w-1.))) * size, float(Math.GetRandomNumber(int(h-1.)))*size)
        else
            let (x,y) = position snake.[0]
            let (x',y') = position apple
            if x = x' && y = y' then
                let segment = Shapes.AddRectangle(size,size)
                let dx,dy = directions.[dir]
                Shapes.Move(segment,x+size*dx,y+size*dy)
                snake.Insert(0,segment)
                Shapes.Move(apple, -size, -size)
                spawn_count <- 10
    let go = Shapes.AddText("Game Over")
    Shapes.Move(go, 100, 200)
    Program.Delay(5000)
    Shapes.Remove(go)