You are right. I'm working on War now and probably Go Fish next, neither of which need suits. I figure I'll think of something when I need it. My intuition is filling 'd' with 1 through 52 then in the game logic you would mod 13 for the value and integer divide (\) by four for the suit.

u=unpack --shortening the name of the unpack function

function s(a) --A function to shuffle a stack of cards
    --for each card in a pile, swap it with any card to its right
    for i=1,#a do 
        q=a[i]
        r=i+rnd(#a-i)\1 --i is the index of the card we are swapping, rnd(#a-i)\1 is the number of cards to the right of it
                        --\1, backslash does integer division, which takes the floor of the quotient, is less characters than using flr()
        a[i]=a[r] --the swap
        a[r]=q
    end
    return a --this function doesn't need a return value since it modifies a directly, but I found it useful for shuffling the discard before putting it in your hand
end

function c(a,b) --this function puts a stack of cards, b, on top of the stack of cards, a
    for i=1,#b do
        add(a,b[i]) --adds each card of b in order
    end
end

d={}g={}h={}v={}w=0 --initializing some variables. In order:
                                                            original deck of cards,
                                                            the player's discard pile, 
                                                            the opponent's discard pile, 
                                                            the current cards at stake, 
                                                            how many cards are left to the current war

for i=1,52do d[i]=i end --filling the deck with cards
s(d) --shuffle the deck
x={u(d,1,26)} --the player gets half
y={u(d,27)} --the cpu gets half

Here I use the unpack function to cut the deck by taking a subtable by enclosing the returned tuple with { and }.

::_::        --Usually '_' is used for a label because it would be an awful variable name and so is free
...          --The game loop
flip()goto _ --flip() is necessary to avoid accidentally turning over too many cards

if (#x<1) x=s(g) g={}   --If either player's hand is empty, shuffle their discard and put it in their hand, empty the discard
if (#y<1) y=s(h) h={}

if (#x<1) print('lose') --If either player runs out of cards, the game ends
if (#y<1) print('win')

if (btnp(🅾️) and #x*#y!=0) then --if the player tries to draw a card and the game isn't over (if either #x or #y are zero, their product is also zero)

o=x[#x]%13 --o and p are the top cards of each player's hand
p=y[#y]%13 --we use 13 because we are only concerned with the value, not the suit
c(v,{o,p}) --add the top cards of each player's hand to cards in play
x[#x]=z    --z is an unused uninitialized variable so it is equal to nil
y[#y]=z    --this removes the top cards from the players' hands

if (w<1) then --are we currently in a "war"?

If we aren't in a war then

if (#v<3) cls() --if there are only two cards in play, then a new round has begun and we clear the screen
?'1:'..o..' 2:'..p --reveal the cards
if(o==p)then --if doubles, start a war
    w=3 --set the number of cards left to draw for a war to 3
else --not doubles
    if (o>p) c(g,v) else c(h,v) --If the player wins, they get the cards on the table put in their discard pile
    v={} --empty the table
    ?'s:'..(#x+#g-#y-#h)/2+26 --the round is over, display how many cards the player currently has
end

If we are in a war

?sub('raw',w,w) --prints the letters of war one at a time
w-=1            --reduce the number of cards left in the war
                --we have already drawn the card at the beginning of the game loop

I've commented every line, I'll go back through and point out some tweetcart tricks.