The Strategy of Beating Mastermind Restricted

Refer to the original manual here for the instructions.

The Base Strategy

You may have been familiar with brute forcing the original module before by querying individual LEDs. Unfortunately, this module will punish that technique due to the limited amount of queries required to solve. Luckily there are some tips that can help you solve it more efficiently. This page will go step-by-step of the method the tester used to disarm this module. On average this can take 6 - 8 queries.

1. Start by just pressing the query button on all whites.
2. Take note of how many whites are in their correct positions. This will be referred to as X for this next step.
3. Now query 4 - X magenta LEDs of any combination on the module.
4. If the middle screen now displays a non-zero value, swap the white LED(s) and the magenta LED(s) until the middle screen displays 0. Refer to the left number now as a new X value. Otherwise, skip to step 5.
5. Do not modify the white LEDs now as these are now in their correct positions. Query 4 - X yellows, while avoiding to toggle the white LEDs.
6. Repeat step 4 except with the yellow and magenta LEDs.
7. Keep repeating this procedure with a different color until you get the left number to display a 4.

You may swap to use different sets of colors in the technique mentioned before (I.E swapping white with red, magenta with blue, etc.) however failing to follow the steps correctly may result in wasted queries which can lead to a strike.

Other Tips

Query				Result
W	W	W	W	0, 0
M	M	M	M	2, 0
Y	M	M	Y	0, 2
M	Y	Y	M	2, 0
M	G	G	M	3, 0
M	G	R	M	2, 1
M	R	G	M	3, 0
M	B	G	M	4, 0

If you know that in one of the queries, you get 2 correct colors in the correct positions that are colored the same and somewhere in the next batch of queries, you get 2 correct colors not in the correct positions, like in queries 3 and 4 from the table provided, you should already know where the correct colors are in the respective positions. Likewise, if you know if there are 0 of 1 set of correct colors, it is invaluable to query extras of those colors and just move on to the next color.

Mastermind Restricted Example Scenarios

Example procedures will refer the result of the query as “A, B”, where A is the number of correct colors in their correct positions and B is the number of correct colors not in their correct positions. Any “*” give out major clues to the correct sequence in those example procedures.

Example Procedure #1
Query				Result	Thought Process
W	W	W	W	0, 0	No whites anywhere. I should query all magentas then.
M	M	M	M	1, 0	1 M. I should do 3 Y next and work with the 1 M.
Y	Y	Y	M*	1, 2	Okay. My magenta is definitely not in that location. I think that one contains yellow for sure.
Y	Y	M*	Y	1, 2	That one is also yellow.
Y*	M	Y	Y	2, 1	I think I know where magenta should go. Let’s query the rest of the colors and hope for the best.
M	G	Y	Y	3, 0
M	R	Y	Y	4, 0 (solved)

Example Procedure #2
Query				Result	Thought Process
B	B	B	B	3, 0	3 blues right off the bat. There is only 1 color left on this.
W*	B	B	B	2, 1	I think 1st LED there is blue.
B	W	B*	B*	3, 0	Okay. All of my blues are now set. All that is left is the missing color.
B	M	B	B	3, 0
B	Y	B	B	4, 0 (solved)