-- title: Space Invaders
-- author: Bob Grant
-- desc: Lesson 7
-- script: lua
playerShip = {
position = {
x = 120,
y = 128
},
spriteNum = 0,
minX = 0,
maxX = 232,
speed = 1,
bulletOffset = {
x = 4,
y = 4
}
}
playerBullet = {
position = {
x = 0,
y = 0
},
length = 5,
colour = 14,
speed = 2,
active = false
}
function TIC()
cls()
movePlayerShip()
checkPlayerFire()
movePlayerBullet()
drawPlayerBullet()
drawPlayerShip()
end -- end TIC
function movePlayerShip()
-- check move right button
if(btn(2)) then
playerShip.position.x =
playerShip.position.x - playerShip.speed
end
-- check move left button
if(btn(3)) then
playerShip.position.x =
playerShip.position.x + playerShip.speed
end
playerShip.position.x = checkLimits(
playerShip.position.x,
playerShip.minX,
playerShip.maxX )
end -- movePlayerShip
function checkLimits(value, min, max)
if (value > max) then
value = max
elseif (value < min) then
value = min
else
value = value
end
return value
end -- checkLimits
function checkPlayerFire()
if (not playerBullet.active) then
-- check if the fire button is pressed
if (btnp(4)) then
-- if pressed make a bullet appear
-- at the player ship
playerBullet.position = {
x = playerShip.position.x + playerShip.bulletOffset.x,
y = playerShip.position.y + playerShip.bulletOffset.y
}
playerBullet.active = true
end
end -- not active
end -- checkPlayerFire
function movePlayerBullet()
if (playerBullet.active) then
-- move the bullet up the screen
playerBullet.position.y =
playerBullet.position.y - playerBullet.speed
if (playerBullet.position.y < 0) then
playerBullet.active = false
end
end
end -- movePlayerBullet
function drawPlayerBullet()
if (playerBullet.active) then
-- draw player bullet
-- line(startX, StartY, endX, endY, colour)
line(
playerBullet.position.x,
playerBullet.position.y,
playerBullet.position.x,
playerBullet.position.y + playerBullet.length,
playerBullet.colour
)
end
end -- drawPlayerBullet
function drawPlayerShip()
spr(playerShip.spriteNum,
playerShip.position.x,
playerShip.position.y, 0)
end -- drawPlayerShip
