Lua remove crates - lua

Question

I'm trying to make a simple game but i have ome problems.
I have a game and there is a layer of 6 boxes, 5 sec later there is another layer of 6 boxes and so on..
My problem is that i want to remove 2 random boxes from each layer. in the first layer there will be some kind of object that can jump on the boxes so i want to remove 2 boxes in the first layer and put an object there lik an animal. this is the code that i have (it's only for the first layer of boxes but when i know how to do the first layer it will also work on the second layer)
local physics = require("physics")
physics.start()
display.setDrawMode("hybrid")
local sky = display.newImage("bkg_clouds.png")
sky.x = display.contentWidth/2
sky.y = display.contentHeight/2-60
local ground = display.newImage("ground.png")
ground.x = display.contentWidth/2
ground.y = sky.y + display.contentHeight/2 + 80
ground.rotation = 0.7
local image_outline = graphics.newOutline( 2, "ground.png" )
physics.addBody( ground , "static", {friction = 0.5, bounce = 0.2, outline = image_outline})
local leftwall = display.newRect(0,0,1,display.contentHeight*2+100)
local rightwall = display.newRect(display.contentWidth,0,1,display.contentHeight*2+100)
physics.addBody(leftwall, "static",{bounce=0.1})
physics.addBody(rightwall, "static", {bounce = 0.1})
for i = 27, display.contentWidth-20, display.contentWidth/6 do
local crate = display.newImage("crate.png")
crate.x = i
crate.width = display.contentWidth/6.5
crate.y = 50
crate.height = display.contentWidth/6.5
physics.addBody(crate, {density = 3.0, friction = 0.5, bounce = 0.1})
end

Answer 1

This is probably a really basic solution, but the first thing that comes to mind is generating 2 random indeces you want to use to replace the crates.
So when your loop counter matches the index, then you draw an animal instad of a create.
I was thinking about something like this:
local physics = require("physics")
local math = require("math") -- not sure if you need to require it.
physics.start()
display.setDrawMode("hybrid")
local sky = display.newImage("bkg_clouds.png")
sky.x = display.contentWidth/2
sky.y = display.contentHeight/2-60
local ground = display.newImage("ground.png")
ground.x = display.contentWidth/2
ground.y = sky.y + display.contentHeight/2 + 80
ground.rotation = 0.7
local image_outline = graphics.newOutline( 2, "ground.png" )
physics.addBody( ground , "static", {friction = 0.5, bounce = 0.2, outline = image_outline})
local leftwall = display.newRect(0,0,1,display.contentHeight*2+100)
local rightwall = display.newRect(display.contentWidth,0,1,display.contentHeight*2+100)
physics.addBody(leftwall, "static",{bounce=0.1})
physics.addBody(rightwall, "static", {bounce = 0.1})
-- Generates 2 random indeces, falling in the loop boundary
local index_1 = math.random(27, display.contentWidth-20)
local index_2 = math.random(27, display.contentWidth-20)
for i = 27, display.contentWidth-20, display.contentWidth/6 do
-- Draw animal for matching index, otherwise a crate.
if (i == index_1 or i == index_w) then
-- draw animal
else
local crate = display.newImage("crate.png")
crate.x = i
crate.width = display.contentWidth/6.5
crate.y = 50
crate.height = display.contentWidth/6.5
physics.addBody(crate, {density = 3.0, friction = 0.5, bounce = 0.1})
end
end
As I said, really basic implementation, but should get the trick working for your layer.
Open issues for the implementation:
You might have a layer without animals, as your index might not fall in your generated steps.
Your indeces might overlap, resulting in one animal
Your index might be at the start or end only, altering/beaking your game.
But I'll leave it up to you to deal with those checks.