Card Battle IV

Review — where we got to 5 min

• A swap needs a third box, and three lists in step swap all together.
• A pass floats the biggest card to the top.
• Bubble sort is passes until one goes by with no swaps.

Quick-fire

Your sort does twelve swaps with random row numbers instead of comparing anything. What have you built?

Today’s Topic 3 min

• A round: one comparison, one point
• A shuffle: the swap with random row numbers
• Cards leaving the deck as they are played
• A leaderboard sorted with Lesson 3-11’s sort, and item # of as a place

Learning outcome

By the end of this lesson you will be able to:

1. Shuffle a list.
2. Run a match of several rounds, taking cards out of the deck as they are played.
3. Sort a leaderboard and read a finishing position off it.

Learnt — playing the deck 28 min

1 · A round is one comparison

You have a card. They have a card. Whichever power is bigger wins the round. That is the whole game, and it is an if / else:

set [my power v] to (item (1) of [powers v])
set [their power v] to (item (2) of [powers v])
if <(my power) > (their power)> then
  change [my score v] by (1)
  say [Mine!] for (1) seconds
else
  change [their score v] by (1)
  say [Theirs.] for (1) seconds
end
            

2 · A shuffle is a swap with no opinion

Your sort swaps two rows when they are the wrong way round. Take the comparison out, pick the two rows at random, and do it a dozen times:

repeat (12)
  set [a v] to (pick random (1) to (length of [names v]))
  set [b v] to (pick random (1) to (length of [names v]))
  set [hold name v] to (item (a) of [names v])
  set [hold power v] to (item (a) of [powers v])
  set [hold pic v] to (item (a) of [pics v])
  replace item (a) of [names v] with (item (b) of [names v])
  replace item (a) of [powers v] with (item (b) of [powers v])
  replace item (a) of [pics v] with (item (b) of [pics v])
  replace item (b) of [names v] with (hold name)
  replace item (b) of [powers v] with (hold power)
  replace item (b) of [pics v] with (hold pic)
end
            

3 · Cards leave the deck

Two cards are played each round, so two cards leave — and they leave all three lists, from row 1, twice:

delete (1) of [names v]
delete (1) of [powers v]
delete (1) of [pics v]
delete (1) of [names v]
delete (1) of [powers v]
delete (1) of [pics v]
            

Basic — the whole match 24 min

Open your deck. Two card sprites this time: yours and theirs.

Step 1 — two slots

1. Duplicate your card sprite and call the copy Theirs.
2. Put one in each slot on the table.

Step 2 — the shuffle

1. Make a and b.
2. Build the twelve-swap shuffle under the green flag, after the deck is stocked.
3. Run it a few times and watch the list box.

Step 3 — one round

1. Make my power, their power, my score and their score.
2. Show your card as row 1 and broadcast so theirs shows row 2.
3. Compare the two powers and give the point.

Step 4 — three rounds

1. Wrap the round in repeat (3).
2. At the bottom of the round, delete rows 1 and 2 from all three lists.
3. Show a round counter on the Stage.

Step 5 — a winner

1. After the loop, compare the two scores.
2. Say who won and by what.

repeat (3)
  change [round v] by (1)
  switch costume to (item (1) of [pics v])
  set [my power v] to (item (1) of [powers v])
  set [their power v] to (item (2) of [powers v])
  broadcast [their card v]
  say (join (item (1) of [names v]) (join [ ] (join (my power) (join [ vs ] (their power))))) for (1.5) seconds
  if <(my power) > (their power)> then
    change [my score v] by (1)
  else
    change [their score v] by (1)
  end
  delete (1) of [names v] // and the same for powers and pics
  delete (1) of [names v] // twice over - two cards were played
end
            

A leaderboard

Four players, four scores, and the board put in order.

• Two lists in step: players and scores.
• The bubble sort from Lesson 3-11, pointed at the scores.
• The winner is row 1 when it finishes.

Where did I come?

Once the board is sorted, a row number means something new.

• Ask for a player’s name.
• Say what place they came, out of how many.
• Somebody who did not play is told so.

set [place v] to (item # of (who) in [players v])
            

The podium

Show the top three, with no searching at all.

• First, second and third, in that order.
• Each with their score.
• No loop that looks for the biggest — you already sorted it.

Ship it

Put the whole arc together into a game somebody else can play, and share it. This is the end of the run — make it something you would show people.

• A title, a shuffled deck, and a match of three rounds.
• Your score added to a leaderboard.
• The board sorted, and your place read off it.
• A play-again key.

add [Mia] to [players v]
add (my score) to [scores v]
broadcast [sort the board v] // the bubble sort from Lesson 3-11
set [place v] to (item # of [Mia] in [players v])
say (join [Mia came ] (join (place) (join [ of ] (length of [players v])))) for (3) seconds
            

Summary 5 min

• A round is one comparison; a match is a loop of rounds.
• A shuffle is the swap with random row numbers and no comparison.
• Cards played leave all the lists they are in, from row 1.
• A sorted leaderboard turns (item # of () in [players v]) into a finishing place.
• Sorting is paid once and makes many questions free — top three, last, who came third.

Shuffle

Putting a list into a random order.

Round

One turn of a game, decided by one comparison.

Leaderboard

A list of players and scores, kept in order.

Place

A row number on a sorted list.

Hand in

Share your finished game and send the link to your teacher. It should shuffle, deal, play a match, record the score and rank the board.

That is twelve lessons and three games. You have written two algorithms with names — linear search and bubble sort — and they are the same two a computer science exam will ask you about in a few years’ time.