Castle Climb II

Review — Castle Climb I 5 min

• tile at (x) (y) :: custom turns a point into col, row and the letter in tile.
• Four corners say if the knight is inside a brick.
• Landing puts the knight 12 above the top of its row. The top of row r is 210 − 30 × r.

Quick-fire

The knight’s feet land in row 9. What y does the knight stand at?

Today’s Topic 3 min

• Three levels, kept as three save codes in one list
• unpack code :: custom — Tile Maker’s, now run by the knight
• find start :: custom — search the map for the S
• E loads the next level. ^ sends you back to the start.

Learning outcome

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

1. Keep several levels in one list and load any of them by its number.
2. Find where a letter is by scanning the whole map.
3. Make tiles that do something when the knight reaches them.

Learnt — three floors 30 min

1 · Three levels, one list

A save code is a whole level in one line: the 12 rows joined, 192 letters. So three levels fit in a list of three items, called levels. A variable, level number, says which one we are on.

levels
  1  #################..............##..............##..............##..............##..............##..............##..............##..............##.........#....##S....^...#...E#################
  2  #################..............##.............E##...........#####..............##.......###....##..............##...###........##..............##.##...........##S##...^^^^^^^.#################
  3  #################E.............######..........##..............##.....####.....##..........###.##..............##......###.....##..............##...##.........##S..##^^^^^^^^.#################

1. Make a list for all sprites called levels.
2. In its monitor on the Stage, click + three times.
3. Paste one code into each item. Scroll the box above to copy them, or use your own: in Tile Maker press C, and copy the code out of the save code list.

2 · Unpacking a code

The game still reads the level list, one row at a time. So a code has to be cut back into 12 rows of 16 letters — and you already wrote the block that does it, in Tile Maker IV. Give the knight its own copy, with the counters called r and c (the knight’s col and row belong to tile at (x) (y) :: custom).

define unpack code
delete all of [level v]
set [r v] to (1)
repeat (12)
  set [new row v] to []
  set [c v] to (1)
  repeat (16)
    set [new row v] to (join (new row) (letter ((((r) - (1)) * (16)) + (c)) of (code)))
    change [c v] by (1)
  end
  add (new row) to [level v]
  change [r v] by (1)
end
            

3 · Finding the start

Every map has one S, but not in the same place. Read every cell. When the letter is S, keep that cell’s centre in start x and start y.

define find start
set [r v] to (1)
repeat (12)
  set [c v] to (1)
  repeat (16)
    if <(letter (c) of (item (r) of [level v])) = [S]> then
      set [start x v] to ((-225) + ((30) * ((c) - (1))))
      set [start y v] to ((165) - ((30) * ((r) - (1))))
    end
    change [c v] by (1)
  end
  change [r v] by (1)
end
              

define start level
set [code v] to (item (level number) of [levels v])
unpack code :: custom
find start :: custom
go to x: (start x) y: (start y)
set [y velocity v] to (0)
broadcast [redraw v]
              

r and c on the knight are for this sprite only. Tile has its own pair, so the two sprites’ loops can never mix up each other’s count.

4 · The exit

After every fall, ask what is at the knight’s middle. If it is E, move on to the next level — unless that was the last one.

define check tiles
tile at (x position) ((y position) - (6)) :: custom
if <<(tile) = [^]> or <(y position) < (-170)>> then
  go to x: (start x) y: (start y)
  set [y velocity v] to (0)
end
tile at (x position) (y position) :: custom
if <(tile) = [E]> then
  next level :: custom
end
              

define next level
change [level number v] by (1)
if <(level number) > (length of [levels v])> then
  say [You climbed the castle!] for (3) seconds
  stop [all v]
end
start level :: custom
              

5 · Spikes

The spike art fills the bottom of its cell, so the check is 6 below the knight’s middle. Falling off the bottom of the Stage counts too: <(y position) < (-170)>.

Basic — a three-floor climb 25 min

Carry on from your Castle Climb I project.

Step 1 — the codes

1. Make the levels list and paste in the three codes (or three of your own).
2. Make variables for all sprites: level number, start x, start y, code, new row.
3. On the knight, make r and c for this sprite only.

Step 2 — Tile draws on request

1. Take load level :: custom and draw level :: custom out of the Tile green-flag script — the knight loads levels now. Leave hide there.
2. Add when I receive [redraw v] with draw level :: custom under it.

Step 3 — the knight’s new My Blocks

1. Make unpack code :: custom, find start :: custom and start level :: custom.
2. Make check tiles :: custom and next level :: custom. Leave these two unticked: one of them waits three seconds.

Step 4 — the green flag

1. Change the knight’s hat to when flag clicked.
2. Replace the go to with level 1 and start level.
3. Add check tiles :: custom after fall :: custom, inside the forever.
4. Climb all three floors.

when flag clicked
set rotation style [left-right v]
set size to (18) %
point in direction (90)
set [level number v] to (1)
start level :: custom
forever
  if <key (right arrow v) pressed?> then
    point in direction (90)
    walk (4) :: custom
  end
  if <key (left arrow v) pressed?> then
    point in direction (-90)
    walk (-4) :: custom
  end
  if <<key (space v) pressed?> and <(on ground) = (1)>> then
    set [y velocity v] to (12)
  end
  fall :: custom
  check tiles :: custom
end
            

A floor banner

Tell the player which floor they have reached.

• As each floor starts, the knight says Floor 1, Floor 2 or Floor 3 for two seconds.
• The player can walk while the banner shows.

when I receive [banner v]
say (join [Floor ] (level number)) for (2) seconds
            

A fourth floor

Add a level of your own. The game must notice without being told.

• Add a fourth code to levels: one from your Tile Maker, or this one.
• The banner says Floor 1 of 4, and so on.
• The game ends after the last floor. No number in the code says 4.

#################..............##..............##..............##..............##..............##..............##..............##.........##...##.....##..##...##S.^..##..##.^E#################

when I receive [banner v]
say (join (join [Floor ] (level number)) (join [ of ] (length of [levels v]))) for (2) seconds
            

A level select for testing

Testing floor 3 should not mean climbing floors 1 and 2 every time.

• Press 1, 2 or 3 to jump straight to that floor, drawn, with the knight on its S.
• Press N to skip to the next floor.
• The knight is never left falling, or stuck in a wall, after a jump.

when [3 v] key pressed
set [level number v] to (3)
start level :: custom

when [n v] key pressed
next level :: custom
            

A time for every floor

Speed-runners want to know which floor slows them down.

• A list called times, empty at the green flag.
• Each time a floor is finished, its time in whole seconds is added to the list.
• A floor’s time starts when that floor starts, not at the green flag.

define next level
add (round ((timer) - (floor start))) to [times v]
set [floor start v] to (timer)
change [level number v] by (1)
if <(level number) > (length of [levels v])> then
  say [Three floors, three times.] for (3) seconds
  stop [all v]
end
start level :: custom
            

Summary 5 min

• A whole level fits in one save code, so many levels fit in one list.
• unpack code :: custom cuts a code back into 12 rows of 16.
• Scanning every cell finds a letter; the cell gives its centre.
• Letters can do things: E loads the next floor, ^ sends you back.

Save code

A whole level written as one line of letters.

Unpack

Turning a packed-up form back into the form a program uses.

Scan

Checking every cell in turn, row by row.

Respawn

Coming back to the start after losing.

Hand in

Save your three-floor climb. Next lesson the map starts changing while you play: coins vanish, keys open doors, and flags move your restart.