Tour de Four (https://www.puzzlescript.net/play.html?p=a0e76a8e69c31c4f5e7440d6d4e679a4)

script.txt

title  Tour de Four
author Chris Pickel
homepage sfiera.net
again_interval 0.08
background_color #222

========
OBJECTS
========

Background .
Black

Player @
White Black
.000.
.010.
00000
.000.
.0.0.

Red R
Red DarkRed
00000
00000
00100
00000
00000

Blue B
Blue Purple
00000
00000
01010
00000
00000

Yellow Y
Yellow Brown
00000
00100
00000
01010
00000

Cleared
White
.....
.0.0.
..0..
.0.0.
.....

Unchecked
Transparent

Checking
Transparent

One
Transparent

Two
Transparent

Three
Transparent

Four
Transparent

=======
LEGEND
=======

Block   = Red or Blue or Yellow
Movable = Player or Block
Number  = One or Two or Three or Four

=======
SOUNDS
=======

Block   move   34341907
Cleared create 3567303
endlevel       18798902

================
COLLISIONLAYERS
================

Background
Player, Block, Cleared
Unchecked, Checking
Number

======
RULES     
======     

(clear blocks after “again” happens)
[Cleared] -> []

(push transitively)
[> Movable | Movable] -> [> Movable | > Movable]

(mark all blocks for checking)
late [Block] ->  [Unchecked Block]

startloop
(pick a random origin block)
late random [Unchecked Block] -> [One Checking Block]

(flood fill across like-colored blocks, incrementing up to four)
late [One]   [Checking Red    | Unchecked Red   ] -> [Two]   [Checking Red    | Checking Red   ]
late [Two]   [Checking Red    | Unchecked Red   ] -> [Three] [Checking Red    | Checking Red   ]
late [Three] [Checking Red    | Unchecked Red   ] -> [Four]  [Checking Red    | Checking Red   ]
late         [Checking Red    | Unchecked Red   ] ->         [Checking Red    | Checking Red   ]
late [One]   [Checking Blue   | Unchecked Blue  ] -> [Two]   [Checking Blue   | Checking Blue  ]
late [Two]   [Checking Blue   | Unchecked Blue  ] -> [Three] [Checking Blue   | Checking Blue  ]
late [Three] [Checking Blue   | Unchecked Blue  ] -> [Four]  [Checking Blue   | Checking Blue  ]
late         [Checking Blue   | Unchecked Blue  ] ->         [Checking Blue   | Checking Blue  ]
late [One]   [Checking Yellow | Unchecked Yellow] -> [Two]   [Checking Yellow | Checking Yellow]
late [Two]   [Checking Yellow | Unchecked Yellow] -> [Three] [Checking Yellow | Checking Yellow]
late [Three] [Checking Yellow | Unchecked Yellow] -> [Four]  [Checking Yellow | Checking Yellow]
late         [Checking Yellow | Unchecked Yellow] ->         [Checking Yellow | Checking Yellow]

(if four was reached, mark all blocks that were checked this time through to be cleared during “again”)
late [Four] [Checking] -> [Four] [Cleared] again

(otherwise clean up everything in preparation for another iteration)
late [] -> [no Number no Checking]

endloop

==============
WINCONDITIONS
==============

No Block
No Cleared

=======     
LEVELS
=======

@....
.R.R.
.....
.R.R.
.....

@....
.RBR.
.B.B.
.RBR.
.....

@.....
.RBRB.
.BRBR.
.RBRB.
.BRBR.
......

@....BRB
.RBR..BR
..BRB..B
R..RBR..
BR..BRB.
RBR.....

@..BRB
RBR.BR
.BRB.B
R.RBR.
BR.BRB
RBR...

@....
.RRR.
.....
.RRR.
.....

@.....
..BR..
.BRBR.
.RBRB.
..RB..
......

@...B
..BRB
.R.R.
.BB..
RR...

@.....
.BBRR.
.RRYY.
.YYRR.
.RRBB.
......

@......
...Y...
..RBR..
.YBYBY.
..RBR..
...Y...
.......

@..Y...
..RBR..
.YBYBY.
..RBR..
...Y...

@.....
.RBYR.
.YRBY.
.BYRB.
.RBYR.
......

@....Y
.RYYB.
.YRBY.
.YBRY.
.BYYR.
Y....Y