Small Mob Farm

-- Configuration
local MONITOR_SIDE = "top"
local REDSTONE_SIDE = "bottom"
local STATUS_FILE = "farmStatus"

-- Colors
local COLOR_RUNNING = colors.red
local COLOR_STOPPED = colors.green
local COLOR_BG = colors.black
local COLOR_TEXT = colors.white
local COLOR_BUTTON = colors.lime
local COLOR_GROUND = colors.purple
local COLOR_CREEPER = colors.lime
local COLOR_X = colors.red

-- Monitor setup
local monitor = peripheral.wrap(MONITOR_SIDE)
monitor.setTextScale(1)
local w, h = monitor.getSize()

-- State
local farmRunning = false
local creeperX = w - 3
local blink = true

-- Save/load
local function saveStatus()
    local f = fs.open(STATUS_FILE, "w")
    f.write(farmRunning and "running" or "stopped")
    f.close()
end

local function loadStatus()
    if fs.exists(STATUS_FILE) then
        local f = fs.open(STATUS_FILE, "r")
        local data = f.readAll()
        f.close()
        return data == "running"
    end
    return false
end

-- Redstone
local function updateRedstone()
    redstone.setOutput(REDSTONE_SIDE, not farmRunning)
end

-- Draw 3-line header with centered label
local function drawHeader()
    local label = farmRunning and "RUNNING" or "STOPPED"
    monitor.setBackgroundColor(farmRunning and COLOR_RUNNING or COLOR_STOPPED)
    monitor.setTextColor(COLOR_TEXT)
    for y = 1, 3 do
        monitor.setCursorPos(1, y)
        monitor.write((" "):rep(w))
    end
    local x = math.floor((w - #label) / 2) + 1
    monitor.setCursorPos(x, 2) -- Middle line
    monitor.write(label)
end

-- Button
local function drawButton()
    local label = farmRunning and "STOP" or "START"
    local x = math.floor((w - #label) / 2) + 1
    monitor.setCursorPos(x, 5)
    monitor.setBackgroundColor(COLOR_BUTTON)
    monitor.setTextColor(COLOR_TEXT)
    monitor.write(label)
end

-- Button check
local function isButtonPressed(x, y)
    return y == 5
end

-- Draw purple ground line at bottom
local function drawGround()
    monitor.setCursorPos(1, h)
    monitor.setTextColor(COLOR_GROUND)
    monitor.setBackgroundColor(COLOR_BG)
    monitor.write(("⯀"):rep(w))
end

-- Clear creeper line (above ground)
local function clearCreeperRow()
    monitor.setCursorPos(1, h - 1)
    monitor.setBackgroundColor(COLOR_BG)
    monitor.write((" "):rep(w))
end

-- Draw creeper frame
local function drawCreeper()
    clearCreeperRow()
    if creeperX > 3 then
        monitor.setCursorPos(creeperX, h - 1)
        monitor.setTextColor(COLOR_CREEPER)
        monitor.write("C")
    elseif creeperX == 3 then
        monitor.setCursorPos(creeperX, h - 1)
        monitor.setTextColor(COLOR_X)
        monitor.write("X")
        sleep(0.5)
        clearCreeperRow()
    end
end

-- Safe to enter (stopped)
local function drawSafeBlink()
    local msg = "SAFE TO ENTER"
    local x = math.floor((w - #msg) / 2) + 1
    monitor.setCursorPos(x, h - 1)
    monitor.setBackgroundColor(COLOR_BG)
    monitor.setTextColor(COLOR_STOPPED)
    if blink then
        monitor.write(msg)
    else
        monitor.write((" "):rep(#msg))
    end
end

-- Full screen draw
local function redraw()
    monitor.setBackgroundColor(COLOR_BG)
    monitor.clear()
    drawHeader()
    drawButton()
    drawGround()
end

-- Init
farmRunning = loadStatus()
updateRedstone()
redraw()

-- Parallel logic
parallel.waitForAny(
    function() -- Animation
        while true do
            if farmRunning then
                drawGround()
                drawCreeper()
                creeperX = creeperX - 1
                if creeperX < 3 then
                    creeperX = w - 3
                end
            else
                drawGround()
                drawSafeBlink()
                blink = not blink
            end
            sleep(0.3)
        end
    end,
    function() -- Touch handler
        while true do
            local _, _, x, y = os.pullEvent("monitor_touch")
            if isButtonPressed(x, y) then
                farmRunning = not farmRunning
                creeperX = w - 3
                saveStatus()
                updateRedstone()
                redraw()
            end
        end
    end
)