local buttons = {
    [1] = {
        x = 3,
        y = 3,
        on_state = "Turn off reactor",
        off_state = "Turn on reactor",
        current_state = true, -- Initially the button is off
        onClick = function(state) -- Turn the reactor on or off
            if state then -- Currently on, turning off
            	term.setCursorPos(1,1)
            	term.write("Turning off the reactor")
            	sleep(1)
                -- The current state is off: turn off the reactor
            else
            	term.setCursorPos(1,1)
            	term.write("Turning on the reactor")
            	sleep(1)
                -- The current state is off: turn on the reactor
            end
        end
    }
}

local function drawButton(button)
    term.setCursorPos(button.x, button.y)
    if button.current_state then -- If it’s on, our button is green
        term.setBackgroundColor(colors.green)
    else -- Otherwise it’s red
        term.setBackgroundColor(colors.red)
    end

    term.setTextColor(colors.white)

    local button_text -- We’ll store what text we want to write here
    if button.current_state then
        button_text = button.on_state
    else
        button_text = button.off_state
    end

    local button_length = #button.on_state -- How long is our button?
    if #button.off_state > #button.on_state then -- We want the longest it ever gets
        button_length = #button.off_state
    end

    term.write(string.rep(" ", 2 + button_length)) -- Give it a little space on each side
    term.setCursorPos(button.x + 1 + button_length / 2 -
        #button_text / 2, button.y) -- Nothing too complicated here: just centering the text inside of the button
    term.write(button_text) -- Draw our text
end

local function checkClick(x, y)
    for index, button in pairs(buttons) do
        local button_length = #button.on_state + 2
        if #button.off_state > #button.on_state then
            button_length = #button.off_state + 2
        end

        if button.y == y and
            x >= button.x and
            x <= button.x + button_length then
            -- Yep, we clicked this button
            button.onClick(button.current_state)
            button.current_state = not button.current_state
        end
    end
end

while true do
    term.setBackgroundColor(colors.black)
    term.clear()
    for index, button in pairs(buttons) do drawButton(button) end
    local e = {os.pullEvent("mouse_click")} -- Change to "monitor_touch" if you’re working with a monitor
    checkClick(e[3], e[4])
end