Stackerz

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! Score: " .. #stack - 1
        term.setCursorPos( math.floor( (maxx - #str) / 2 ), maxy / 2 )
        print( str )
        term.setCursorPos( 1, 1 )
		sleep(3)
        os.reboot()
end

local function renderStack()
        if #stack - nBase > maxy / 2 then
                nBase = nBase + 1
        end
        term.setBackgroundColor( colors.white )
        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

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 = { 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 ] == "key" and event[ 2 ] == keys.space 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
                                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