Scratch

I don't understand it either but you can just copy the scripts from that other game you were looking at and mess around with it until you get the feel for it, and, if you don't feel like copying, after you have the feel for it create your own script.

For cannon shooting games, I find using x-vel and y-vel to be the simplest (with a constant x-vel and a changing y-vel*).  Finding the initial values for these can be done using trig, but after that initial trig, you really don't need any.

set [x-vel v] to (initial x velocity) // use trig
set [y-vel v] to (initial y velocity) // use trig
repeat until <touching [ground v]?>
change x by (x-vel)
change y by (y-vel)
change [y-vel v] by (-.5)
end

Last edited by MoreGamesNow (2012-04-09 15:32:42)

I know you said you know how to use trig, but for Scratch, the sine and cosine are reverse from normal geometry. So:

xvel = force * sin (angle)
yvel = force * cos (angle)

mythbusteranimator wrote:

O.K., but what is "force," and how do I symbolize it in SCRATCH?

Force is just a multiplier.  The force behind the projectile, just set it to any positive number.  You can think of "force" as "power" if you want.

set [xvel v] to ((force)*([sin v] of (direction)))
set [yvel v] to ((force)*([cos v] of (direction)))
repeat until <touching [edge v]?>
change x by (xvel)
change y by (yvel)
change [yvel v] by (-1)
end

Last edited by MoreGamesNow (2012-04-09 17:33:26)

I'm going to create a game using this (Archery 4) involving bouncing off of walls. Any suggestions involving the bounce off walls and the angles involved? Or is it just

if <touching [wall]
 set [xvel] to (xvel * -1)
 change x by (xvel)
 change y by (yvel)
 

As LS97 said, if the walls are at right angles, you can simply reverse velocities (see script below).  Otherwise, you'll need to know the angle of the wall 

forever
change x by (xvel)
if<touching [wall v]?>
set [xvel v] to ([-1]*(xvel))
end
change y by (yvel)
if<touching [wall v]?>
set [yvel v] to ([-1]*(yvel))
end
end

You first have to find out the slope of the wall at the point they collided.  This is pretty much impossible to find with any amount of accuracy.  You could make the walls different colors (visually unappealing  ) or try to approximate it with sensing (a special sensing costume perhaps?).  Either way, it will be challenging.  After that, some trig should do it (you always bounce at the same angle, relative to the wall, as you approached it at).

Last edited by MoreGamesNow (2012-04-10 13:28:46)

This script should work (goes in the ball/arrow).

when gf clicked
set [power v] to [0]
set [x-vel v] to [0]
set [y-vel v] to [0]
go to x: [-64] y: [-14]
forever
repeat until <mouse down?>
point towards [mouse-pointer v]
if<<(direction) > [135]> or <(direction) < [45]>>
point in direction [90 v]
end
end
set [power v] to ((distance to [mouse-pointer v])/[8])
set [x-vel v] to ((power)*([sin v] of (direction)))
set [y-vel v] to ((power)*([sin v] of (direction)))
repeat until<<[-160] > ([y position v] of [Ball v])> or <touching [target v]?>>
change x by (x-vel)
change y by (y-vel)
change [y-vel v] by (-1)
if<touching [wall v]?>
set [x-vel v] to ((x-vel)*[-0.5])
change x by (x-vel)
change y by (y-vel)
end
end
if<touching [target v]?>
if<touching color [blue]?>
change [SCORE v] by (20)
else
if<touching color [green]?>
change [SCORE v] by (10)
else
change [SCORE v] by (5)
end
end
end
go to x: [-64] y: [-14]
set [x-vel v] to [0]
set [y-vel v] to [0]
set [power v] to [0]

I believe it is getting stuck in the original forever loop (that gets activated when the green flag is clicked).

Looks good.  Making the wall thicker should get rid of the occasional "pass through wall" glitch.