Can anyone explain this navigation script?

[Kelli3K]

Is anyone able to explain what this script does and (more specifically) HOW it does it? Thankyou.


property pSprite
property pSpeed
property pMaxSpeed
property pFriction
property pRotateAmt

on BeginSprite me
pSprite = me.spriteNum
pSpeed = 0
pMaxSpeed = 18
pFriction = 0.6
pRotateAmt = 10
end

on ExitFrame me
if keyPressed(123) then
sprite(pSprite).rotation = sprite(pSprite).rotation - pRotateAmt
else if keyPressed(124) then
sprite(pSprite).rotation = sprite(pSprite).rotation + pRotateAmt
end if
if keyPressed(126) then
if pSpeed < pMaxSpeed then
pSpeed = pSpeed + 1
end if
else
if pSpeed > 0 then
pSpeed = pSpeed - pFriction
end if
if pSpeed < 0 then
pSpeed = 0
end if
end if

if pSpeed > 0 then
angRad = pi() * sprite(pSprite).rotation/180.0
sprite(pSprite).loc = sprite(pSprite).loc + point(pSpeed * cos(angRad), Â
pSpeed * sin(angRad))
end if
end

 

[chrisrf]

I've added some comments which i hope will help

property pSprite -- declare properties here
property pSpeed
property pMaxSpeed
property pFriction
property pRotateAmt

on BeginSprite me --now set initital values for properties
pSprite = me.spriteNum
pSpeed = 0
pMaxSpeed = 18
pFriction = 0.6
pRotateAmt = 10
end

on ExitFrame me
if keyPressed(123) then --key 123 rotates the sprite anticlockwise
sprite(pSprite).rotation = sprite(pSprite).rotation - pRotateAmt
else if keyPressed(124) then --key 124 rotates the sprite clockwise
sprite(pSprite).rotation = sprite(pSprite).rotation + pRotateAmt
end if
if keyPressed(126) then --key 126 increases the sprites speed upto a max of pMaxSpeed
if pSpeed < pMaxSpeed then
pSpeed = pSpeed + 1
end if
else
if pSpeed > 0 then --if sprite is moving, slow it down (friction)
pSpeed = pSpeed - pFriction
end if
if pSpeed < 0 then --don't allow negative speeds
pSpeed = 0
end if
end if

if pSpeed > 0 then --update sprites position
angRad = pi() * sprite(pSprite).rotation/180.0
sprite(pSprite).loc = sprite(pSprite).loc + point(pSpeed * cos(angRad), Â
pSpeed * sin(angRad))
end if
end