A simple memory game

Arjen Markus Inspired by RS's A funny cookbook I wrote down this script that implements a very basic memory game. In Holland it is actually known as "Memory" - I do not know whether that is the proper English name, though.

The rules are simple: you have a number of pairs of cards and they are put on the table, face down. Each player turns around two of the cards and if he/she has a matching pair, he/she gets them. The winner is of course the player with most pairs.

The script below implements a minimal version:

The pictures are replaced with prozaic numbers
The number of cards is fixed to 20 and the layout is hard-coded
There is only one player
There is no score card

But most of these limitations are easy to fix - see the exercises.

# memorygame.tcl --
#    A basic implementation of the game of "Memory"
#

package require Tk

#
# Set up the buttons (they play the role of the picture cards)
#
set values [list]
for { set i 1 } { $i <= 10 } { incr i } {
    lappend values $i $i
}

for { set i 1 } { $i <= 20 } { incr i } {
    set idx [expr {int(rand()*[llength $values])}]
    set label_text($i) [lindex $values $idx]
    set values [lreplace $values $idx $idx]

    button .b_$i -text " " -command [list showLabel $i] -width 3
}

button .next -text "Next" -command nextMove
label  .empty -text " "

grid   .b_1  .b_2  .b_3  .b_4  .b_5
grid   .b_6  .b_7  .b_8  .b_9  .b_10
grid   .b_11 .b_12 .b_13 .b_14 .b_15
grid   .b_16 .b_17 .b_18 .b_19 .b_20
grid   .empty  .next -     -     -

#
# Initialise
#
set click_count    0
set clicked_values [list]

#
# Handle selections
#
proc showLabel {label} {
    global click_count
    global clicked_values
    global label_text

    if { $click_count >= 2 } { return }

    incr click_count
    .b_$label configure -text $label_text($label)

    lappend clicked_values $label

    if { $click_count == 2 } {
       set label1 [lindex $clicked_values 0]
       set label2 [lindex $clicked_values 1]
       if { $label_text($label1) == $label_text($label2) } {
          foreach label $clicked_values {
             .b_$label configure -state disabled
          }
          set clicked_values [list]
          set click_count    0
       }
    }
}

#
# Handle next move
#
proc nextMove {} {
    global clicked_values
    global click_count

    foreach label $clicked_values {
       .b_$label configure -text " "
    }
    set clicked_values [list]
    set click_count 0
}

Exercises for the young programmers for whom this is meant:

Use names instead of numbers
Can you adjust the game to, say, 15 pairs? 20 pairs? An arbitrary number? (the latter is a bit more difficult) What do you need to change in the code?
Can you come up with a strategy? What is the minimal number of steps?
Add a score card (showing the number of steps so far, and how pairs were found)
For the adventurous: add a second player
For the whizkids: turn this into a tic-tac-toe game

See also Memory 2 which might be more appealing to play, but the code is less simple than the above (though with similarities). I'd however do away with the click_count variable above - the two places where it is tested can use [llength $clicked_values], which should give the same result in all cases, and make the thing simpler again.

Screenshots

gold added pix

Category Education

Category Games