singe/docs/learn/11-hitting-things.singe

-- Lesson 11:  Hitting Things.  The finished script, exactly as the lesson ends.
dofile("Singe/Framework.singe")

local SHIP_WIDTH  = 32
local SHIP_HEIGHT = 24
local SHIP_PAD_X  = 6
local SHIP_PAD_Y  = 5
local SHIP_SPEED  = 3
local ROCK_WIDTH  = 24
local ROCK_HEIGHT = 24
local ROCK_PAD    = 4
local ROCK_SPEED  = 1
local ROCK_CHANCE = 40
local SHOT_WIDTH  = 4
local SHOT_HEIGHT = 10
local SHOT_SPEED  = 6
local SHOW_BOXES  = false

local shipSprite = spriteLoad(DIR .. "art/ship.png")
local rockSprite = spriteLoad(DIR .. "art/rock.png")
local shotSprite = spriteLoad(DIR .. "art/shot.png")
local shootSound = soundLoad(DIR .. "art/shoot.wav")
local boomSound  = soundLoad(DIR .. "art/boom.wav")

local shipX       = (overlayGetWidth() - SHIP_WIDTH) / 2
local shipY       = overlayGetHeight() - SHIP_HEIGHT - 8
local movingLeft  = false
local movingRight = false
local rocks       = {}
local shots       = {}


local function addRock()
    local rock = {}
    rock.x = math.random(0, overlayGetWidth() - ROCK_WIDTH)
    rock.y = -ROCK_HEIGHT
    rocks[#rocks + 1] = rock
end


local function fireShot()
    local shot = {}
    shot.x = shipX + SHIP_WIDTH / 2 - SHOT_WIDTH / 2
    shot.y = shipY - SHOT_HEIGHT
    shots[#shots + 1] = shot
    soundPlay(shootSound)
end


local function rockBox(rock)
    return rock.x + ROCK_PAD, rock.y + ROCK_PAD, ROCK_WIDTH - ROCK_PAD * 2, ROCK_HEIGHT - ROCK_PAD * 2
end


local function shipBox()
    return shipX + SHIP_PAD_X, shipY + SHIP_PAD_Y, SHIP_WIDTH - SHIP_PAD_X * 2, SHIP_HEIGHT - SHIP_PAD_Y * 2
end


local function shipHitsRock(rock)
    local sx, sy, sw, sh = shipBox()
    local rx, ry, rw, rh = rockBox(rock)
    return collideRects(sx, sy, sw, sh, rx, ry, rw, rh)
end


local function shotHitsRock(shot, rock)
    local rx, ry, rw, rh = rockBox(rock)
    return collidePointRect(shot.x + SHOT_WIDTH / 2, shot.y, rx, ry, rw, rh)
end


local function moveShip()
    if movingLeft then
        shipX = shipX - SHIP_SPEED
    end
    if movingRight then
        shipX = shipX + SHIP_SPEED
    end
    if shipX < 0 then
        shipX = 0
    end
    if shipX > overlayGetWidth() - SHIP_WIDTH then
        shipX = overlayGetWidth() - SHIP_WIDTH
    end
end


local function moveRocks()
    if math.random(ROCK_CHANCE) == 1 then
        addRock()
    end
    for i = #rocks, 1, -1 do
        local rock = rocks[i]
        rock.y = rock.y + ROCK_SPEED
        if rock.y > overlayGetHeight() then
            table.remove(rocks, i)
        end
    end
end


local function moveShots()
    for i = #shots, 1, -1 do
        local shot = shots[i]
        shot.y = shot.y - SHOT_SPEED
        if shot.y + SHOT_HEIGHT < 0 then
            table.remove(shots, i)
        end
    end
end


local function checkHits()
    for s = #shots, 1, -1 do
        for r = #rocks, 1, -1 do
            if shotHitsRock(shots[s], rocks[r]) then
                table.remove(rocks, r)
                table.remove(shots, s)
                soundPlay(boomSound)
                break
            end
        end
    end
    for r = #rocks, 1, -1 do
        if shipHitsRock(rocks[r]) then
            table.remove(rocks, r)
            soundPlay(boomSound)
        end
    end
end


local function drawBox(x, y, width, height)
    overlayBox(x, y, x + width - 1, y + height - 1)
end


local function drawBoxes()
    colorForeground(0, 255, 0, 255)
    drawBox(shipBox())
    for _, rock in ipairs(rocks) do
        drawBox(rockBox(rock))
    end
end


function onInputPressed(what)
    if what == SWITCH_LEFT then
        movingLeft = true
    elseif what == SWITCH_RIGHT then
        movingRight = true
    elseif what == SWITCH_BUTTON1 then
        fireShot()
    end
end


function onInputReleased(what)
    if what == SWITCH_LEFT then
        movingLeft = false
    elseif what == SWITCH_RIGHT then
        movingRight = false
    end
end


function onOverlayUpdate()
    overlayClear()

    moveShip()
    moveRocks()
    moveShots()
    checkHits()

    spriteDraw(shipSprite, shipX, shipY)
    for _, rock in ipairs(rocks) do
        spriteDraw(rockSprite, rock.x, rock.y)
    end
    for _, shot in ipairs(shots) do
        spriteDraw(shotSprite, shot.x, shot.y)
    end
    if SHOW_BOXES then
        drawBoxes()
    end

    return OVERLAY_UPDATED
end