Patterns

local x1 = 1
local x2 = 51
local y1 = 1
local y2 = 19
local xStep = 1
local yStep = 1

local charList = {"|", "/", "-", "\\"}

local function ripple(rand)
    local index = 1
    while true do
        local rTimer = os.startTimer(.05)
        local events = {os.pullEvent()}
        if events[1] == "timer" then
            for w = x1, x2, xStep do
                index = rand and math.random(1, #charList) or (index + 1)
                if index > #charList and not rand then index = 1 end
                term.setBackgroundColor(2 ^ math.random(0, 15))
                for h = y1, y2, yStep do
                    term.setCursorPos(w, h)
                    write(charList[index])
                end
            end
        elseif events[1] == "mouse_click" or events[1] == "mouse_drag" then
            if events[2] == 1 then
                x1 = events[3]
                y1 = events[4]
            elseif events[2] == 2 then
                x2 = events[3]
                y2 = events[4]
            end
            term.setBackgroundColor(colors.black)
            term.clear()
        end
        if x1 > x2 then xStep = -1 else xStep = 1 end
        if y1 > y2 then yStep = -1 else yStep = 1 end
    end
end

ripple(false)