letters = {
{[[
phoebe,

i know you looked
forward to the 
fireworks festival
every year but our
travels are going 
to keep us away again
this year. i'm so
sorry.

mom & dad]]},
{[[
phoebe,

i need purified water.
bring it to the hospital.
i'll give you reagent
in return.

-- lenore
]],}
}
letter_idx = 2
letters_offset_x = -10-80
letters_offset_y = 8+8

function letters_move_to(x1, y1, x2, y2)
    return {
        timer = 0,
        active=true,

        before=function(s) 
            letters_offset_x = x1
            letters_offset_y = y1
            sfx(2)
        end,

        update=function(s) 
            letters_offset_x = x1 + (s.timer/0.2)*(x2-x1)
            letters_offset_y = y1 + (s.timer/0.2)*(y2-y1)
            if s.timer > 0.2 then 
                letters_offset_x = x2
                letters_offset_y = y2
                s.active=false 
            end
        end,

        draw=function(s) end,
    }
end

function letters_move_out(x1, y1, x2, y2)
    new = letters_move_to(x1, y1, x2, y2)
    --[[new.draw = function(s) 
        draw_paper(letters_offset_x, letters_offset_y, 128, 128)
        draw_letter_on_paper(letters[letter_idx], letters_offset_x+14, letters_offset_y+4)
    end]]
    return new
end

function flip_away_letter(page)
    return {
        prev_page_idx = page,

        timer = 0,
        t2 = 0,
        active=true,

        before=function(s) 
            sfx(2)
        end,

        update=function(s) 
            if s.timer > 0.2 then s.active=false end
            s.t2 = s.timer
        end,

        draw=function(s)
            local page_flip = 600*s.t2
            local x = letters_offset_x + page_flip
            local y = letters_offset_y + 0.1*page_flip
            draw_paper(x, y, 128, 128)
            draw_letter_on_paper(letters[s.prev_page_idx], x+14, y+4)
        end,
    }
end

function flip_in_letter(page, new_page)
    o = flip_away_letter(new_page)
    f = o.draw
    o.other_page_idx = page
    o.draw = function(s)
        s.t2 = 0.2-s.timer
        draw_paper(letters_offset_x, letters_offset_y, 128, 128)
        draw_letter_on_paper(letters[s.other_page_idx], letters_offset_x+14, letters_offset_y+4)
        f(s)
    end
    return o 
end

function letters_update()
    if btnp(0) and letter_idx > 1 then
        animate(flip_away_letter(letter_idx))
        letter_idx -= 1
    end
    
    if btnp(1) and letter_idx < #letters then
        animate(flip_in_letter(letter_idx, letter_idx+1))
        letter_idx = letter_idx + 1
    end

    if btnp(5) then
        animate(letters_move_out(-10, 8, -10-80, 8+8))
        change_screen(screen_workbench)
    end
end


function letters_draw()
    cls()

    draw_background()
    draw_paper(letters_offset_x, letters_offset_y, 128, 128)
    draw_letter_on_paper(letters[letter_idx], letters_offset_x+14, letters_offset_y+4)
end

function draw_letter_on_paper(letter, x, y)
    color(base_text_color)
    print(letter[1], x, y)
end

screen_letters = {draw=letters_draw, update=letters_update}
screen_letters = screen_conversation({{phoebe_portrait, [[oh jeez my pile of letters!]]}}, 
    function() 
        screen_letters = {draw=letters_draw, update=letters_update}
        change_screen(screen_letters)
    end,
    screen_letters)