Let it snow()

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Hey ChatGPT. It’s 2024, the tree has grown, and other trees have started to grow around it. Also someone has put flashing lights on the trees…

using REPL

function snow(io = stdout)
    # Grab terminal dimensions
    h, w = displaysize(io)
    iob = IOBuffer()
    ioc = IOContext(IOContext(iob, io), :displaysize=>(h,w))
    
    # Clear the screen, move cursor up
    print(io, repeat("\n", h), "\e[$(h)A\e[1G")

    # The grid that holds falling snow
    air = ones(Int, w, h)

    # Snowflake characters (index 1 is empty space)
    flakes = [" ", "*", "❄︎", "❅", "❆"]

    # Small sinusoidal helper to vary snowfall probability
    scsin(t) = ((sin(t) / 2) + 0.5) * (0.1 / 3)
    likelihood(t) = scsin(t) + scsin(t * 1.00001) + scsin(t * 0.9999)

    # Print a single tree line with random “lights”
    function printtreeline(ioc, length_of_line)
        for i in 1:length_of_line
            if rand() < 0.12
                # White light
                printstyled(ioc, "o", color=:white, bold=true)
            else
                # Standard green branch
                printstyled(ioc, "x", color=:green)
            end
        end
    end

    # Draw a single “pine” at (base_row, center_col) with specified height + trunk
    function draw_tree(ioc, base_row, center_col; height=12, trunk_height=3)
        # Print each level from top to bottom
        for lvl in 1:height
            row = base_row - height + lvl
            col = center_col - (lvl - 1)
            
            print(ioc, "\e[$(row);$(col)H")
            printtreeline(ioc, 2*lvl - 1)
        end
        
        # Print trunk
        for trunk_lvl in 1:trunk_height
            row = base_row + trunk_lvl
            print(ioc, "\e[$(row);$(center_col)H")
            printstyled(ioc, "│", color=:reverse)
        end
    end

    try
        while true
            # Update the snowfall in 'air'
            for x in 1:w, y in h:-1:1
                air[x,y] = if y == 1
                    # Spawn new snowflakes at top
                    rand() < likelihood(time()) ? rand(2:length(flakes)) : 1
                elseif y == h
                    # Accumulate at bottom
                    ((rand() < 0.95 && air[x,y] > 1) ||
                     (air[x, y-1] > 1 && rand() < 0.2)) ? 2 : 1
                elseif all(>(1), air[x, y:end]) # melt pile sometimes
                    rand() < 0.95 ? 2 : 1
                elseif (air[x, y-1] > 1 && all(>(1), air[x, (y+1):end]))
                    rand() < 0.1 ? 2 : 1
                else
                    # Normal falling
                    air[x, y-1]
                end
            end

            # Print updated snow
            foreach(space -> print(ioc, flakes[space]), air)

            # Draw main (bigger) tree
            main_tree_height = 14
            trunk_height     = 4
            main_base_row    = h - 2  
            main_center_col  = div(w, 2)
            draw_tree(ioc, main_base_row, main_center_col; 
                      height=main_tree_height, trunk_height=trunk_height)

            # Draw some smaller trees around it
            draw_tree(ioc, main_base_row-2, main_center_col - 20; height=10, trunk_height=3)
            draw_tree(ioc, main_base_row-2, main_center_col + 20; height=10, trunk_height=3)
            draw_tree(ioc, main_base_row-6, main_center_col - 35; height=8,  trunk_height=2)
            draw_tree(ioc, main_base_row-6, main_center_col + 35; height=8,  trunk_height=2)

            # Move cursor home
            print(ioc, "\e[H")

            # REPL banner + prompt
            @static VERSION > v"1.11.0-0" ? REPL.banner(ioc) : Base.banner(ioc)
            printstyled(ioc, "julia> ", color = :green, bold = true)
            println(ioc, "snow()")

            # Flush buffer
            print(io, String(take!(iob)))

            # Slight pause
            sleep(1/8)
        end

    catch e
        isa(e, InterruptException) || rethrow()
    end
    nothing
end
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