startup

term.redirect(peripheral.wrap("top"))
local speaker = peripheral.wrap("right")
local nSize, bNew, nBase, stack, maxx, maxy = 8, true, 0, {}, term.getSize()

stack[ 0 ] = { math.floor( maxx/2 ) - 4, math.floor( maxx/2 ) + 4, bReverse = false }

local function gameOver()
    term.clear()
    local str = "Game Over!  Your Score: " .. #stack - 1
    term.setCursorPos( math.floor( (maxx - #str) / 2 ), maxy / 2 )
    print( str )
    term.setCursorPos( 1, 1 )
    error()
end

local function renderStack()
    if #stack - nBase > maxy / 2 then
        nBase = nBase + 1
    end
    term.setBackgroundColor( colors.red )
    for i = 0, #stack do
        if i + nBase > #stack then
            break
        end
        term.setCursorPos( stack[ i + nBase ][ 1 ], maxy - i )
        term.write( string.rep( " ", stack[ i + nBase ][2] - stack[ i + nBase ][1] ) )
    end
    term.setBackgroundColor( colors.black )

end
speaker.playSound("minecraft:music_disc.pigstep",.7)

local function getInput()
    local new = bNew and { 1, nSize + 1, bReverse = false } or stack[ #stack ]
    local id = os.startTimer( 0.1 * (0.99^#stack) )
    while true do
        local event, side, x, y = { os.pullEvent() }
        if event[ 1 ] == "timer" and event[ 2 ] == id then
            if not new.bReverse then
                new[ 1 ] = new[ 1 ] + 1
                new[ 2 ] = new[ 2 ] + 1
                if new[ 2 ] > maxx then
                    new.bReverse = true
                end
            else
                new[ 1 ] = new[ 1 ] - 1
                new[ 2 ] = new[ 2 ] - 1
                if new[ 1 ] <= 1 then
                    new.bReverse = false
                end
            end
            if bNew then
                stack[ #stack + 1 ] = new
                bNew = false
            end
            break
        elseif event[ 1 ] == "monitor_touch"  then
            if new[ 1 ] < ( bNew and stack[ #stack ][ 1 ] or stack[ #stack - 1 ][ 1 ] ) then
                new[ 1 ] = ( bNew and stack[ #stack ][ 1 ] or stack[ #stack - 1 ][ 1 ] )
            end
            if new[ 2 ] > ( bNew and stack[ #stack ][ 2 ] or stack[ #stack - 1 ][ 2 ] ) then
                new[ 2 ] = ( bNew and stack[ #stack ][ 2 ] or stack[ #stack - 1 ][ 2 ] )
            end
            if new[ 2 ] - new[ 1 ] <= 0 then
                speaker.playSound("minecraft:entity.chicken.death",.3)
                gameOver()
            end
            nSize = new[ 2 ] - new[ 1 ]
            if bNew then
                stack[ #stack + 1 ] = new
            else
                stack[ #stack ] = new
                bNew = true
            end
            break
        end
    end
end

while true do
    term.clear()
    renderStack()
    getInput()
end