Hi,

Welcome to another AppGameKit guide. For this one, we'll be looking at a code example inspired by a user request for some pointers into real time strategy game creation. The code also covers some of the other techniques we've used previously and expands or re-enforces on them.

As before, I've include a video of what you should see and documented the code clearly. You will need the image item0.png that we've used in previous guides, and this should be copied into the projects media folder. As a reminder this can be found in your AppGameKit projects folder, under the examples Sprite/SpriteAnim1.

All you need to do to use this code is to cut and paste it into your AppGameKit IDE. I encourage you to play around with the various settings and values.

To use, click anywhere on your screen, and hold down 'left' mouse or equivalent on your chosen device to drag the lasso. Any sprite covered (selected) by the box will fade until outside of the lasso.

If all has gone well, this is what you should see. At present this demonstration only allows selection from top left to bottom right and bottom right to top left.

I plan to expand on this later, to demonstrate some other, simple but useful RTS elements.



// Project: RTS lasso demo
// Created: 2014-12-05

// set window properties
SetWindowTitle( "RTS lasso demo" )
SetWindowSize( 1024, 768, 0 )

// set display properties
SetVirtualResolution( 1024, 768 )

// set some variable for the corners of the lasso box
global topleftx=0
global toplefty=0
global bottomrighttx=0
global bottomrighty=0

// create a type for the various elements of 'The units'
type sampleunittype
x as float
y as float
angle as integer
sprite as float
lasttime as float
endtype

// set up an array for the units.

dim units[10] as sampleunittype

//load in a sample image so we can see the sprite. This is the default balloon from SpriteAnim1 example that we've used in other demo's.

loadimage(1,"item0.png")

//Make our sprites

for makesprites=1 to 10
//create a sprite with image 1
createsprite(makesprites,1)
//randomly place them on screen
units[makesprites].x=random(30,990)
units[makesprites].y=random(30,710)
// we will be moving them around the screen at random angles to simulate movement
units[makesprites].angle=random(1,360)
//assign a sprite number
units[makesprites].sprite=makesprites
next makesprites

//

// main loop


do


// draw a box, left click and drag the box
if GetpointerState()=0
//if the pointer virtual left mouse click isn't down, move the top left corner to the mouse
topleftx=GetpointerX()
toplefty=GetPointery()
else
//if the pointer virtual left mouse click is down, drag the box.
bottomrightx=GetpointerX()
bottomrighty=GetPointery()
endif


//Make the colour of the box, in this case white
colour1=makecolor(255,255,255)
colour2=makecolor(255,255,255)
colour3=makecolor(255,255,255)
colour4=makecolor(255,255,255)

filled=0

//draw the box,

//topleftx - The X component of the top left corner of the box.
//toplefty - The Y component of the top left corner of the box.
//bottomrightx - The X component of the bottom right corner of the box.
//bottomrighty - The Y component of the bottom right corner of the box.
//color1 - The color to use in the top left corner.
//color2 - The color to use in the top right corner.
//color3 - The color to use in the bottom left corner.
//color4 - The color to use in the botom right corner.
//filled - 1 to draw a filled box, 0 to draw an empty box.

//I encourage you to play with all of the settings to see the different effects.


DrawBox(topleftx,toplefty,bottomrightx,bottomrighty,colour1,colour2,colour3,colour4,filled)

// display and move sprites. Use loop to check if sprite is in the box and colour if covered

for displaysprites=1 to 10

//Is the sprite in within the lasso box? For the purpose of this demo only dragging down to the right and up to the left are checked.
If GetSpriteinBox(units[displaysprites].sprite,topleftx,toplefty,bottomrightx,bottomrighty) or GetSpriteinBox(units[displaysprites].sprite,bottomrightx,bottomrighty,topleftx,toplefty)
SetSpriteColorAlpha(units[displaysprites].sprite,80)
else
SetSpriteColorAlpha(units[displaysprites].sprite,255)
endif
// move sprite by angle
units[displaysprites].x=units[displaysprites].x+sin(units[displaysprites].angle)
units[displaysprites].y=units[displaysprites].y+cos(units[displaysprites].angle)
// change direction every 3 seconds. This sample doesn't check to prevent sprites leaving the screen.
if timer()-units[displaysprites].lasttime>3
//reset the timer
units[displaysprites].lasttime=timer()
// set a new random angle
units[displaysprites].angle=random(1,360)
endif
// Set the sprites new position
SetSpritePosition(units[displaysprites].sprite,units[displaysprites].x,units[displaysprites].y)
next displaysprites

//update screen
sync()


loop