function spawnThem(number, mob, tags)
    num = number
    mobtype = mob
    customtags = tags
    --customtags = 'CustomName:"\"Uncle\"",Attributes:[{Name:generic.maxHealth,Base:100}],Health:100.0f'
    a = 0
    while a <= num do
        commands.exec("summon " .. mobtype .. " ~-10 ~ ~ {" .. customtags .. "}")
        a = a + 1
    end
end
levels = 3
levelsnum = {
5,
10,
20
}
levelsmob = {
"minecraft:zombie",
"minecraft:zombie",
"minecraft:zombie"}
levelstag = {
"",
"",
""}
function startSimulation()
    a = 1
    b = true
    while a <= levels+1 do
        spawnThem(levelsnum[a],levelsmob[a],levelstag[a])
        a=a+1
        while b == true do
            sleep(0.5)
            if (redstone.getInput("left")) == true then
                b = false
            end
        end
        b = true
        print(a)
        print(levels)
        sleep(5)
    end
end
startSimulation()