CodePop

CodePop is Mastermind on a daily timer. A secret code of four colours is set each day, shared by everyone, and you have eight guesses to name it exactly and in order. Six colours are on the palette, red, blue, green, yellow, purple and orange, and after each guess four small pegs appear beside your row to say how close you were. The pegs never say which of your four picks they are talking about, and that omission is the entire game.

1. Tap four of the six colours to build a guess, then press Submit. Two more controls sit on the same row, labelled ← Back and Clear.
2. Read the four pegs to the right of your row. Green means a colour is in the code and in the right position, yellow means a colour is in the code but somewhere else, dark means the colour is not in the code at all.
3. Work out what that summary can and cannot mean, then spend the next of your eight guesses on the question it leaves open.

Mastermind is the purest deduction game ever printed on cardboard, and it has aged perfectly, because anonymous pegs mean the game never does the thinking for you. CodePop keeps that honest and adds the two things the boxed version could not: a shared daily code so everyone is working the same board, and an unlimited practice mode so you can drill openings without wasting it. Expert dropping the no-repeats rule is a genuinely different puzzle rather than just a bigger one, since half your elimination logic stops being valid the moment a colour is allowed to appear twice.

Four pegs per guess, deliberately anonymous. Green counts a colour in the right slot, yellow a colour in the code but out of place, dark a colour that is absent, and which peg belongs to which of your four picks is precisely what the game withholds. The consequence is that no single row tells you much: the information lives in the difference between one guess and the next, which is why the good players here change one thing at a time rather than rebuilding the row every turn.

Daily

One puzzle a day shared by everyone, with a new code at midnight, a shareable result and streaks you can compare with friends.

Practice

Unlimited puzzles on randomly generated codes, offered for warming up or learning strategy.

Standard

The default difficulty. The secret code uses four different colours, with no repeats.

Expert

Colours may repeat in the code, which the game describes as significantly harder.

• Know which difficulty you are reasoning in. Under Standard, a colour that appears once cannot appear again, so every confirmed colour also removes a candidate everywhere else. Expert throws that shortcut away.
• Change one thing at a time once you are past the opening. Swap two colours and watch the peg counts stay identical and you have learned something exact; change three and you have learned almost nothing.
• Count the pegs before you read their colours. If none of the four comes back dark, every colour you played is in the code and the whole problem has collapsed into an ordering question.
• Practice mode is the free laboratory. The codes there are random rather than the day's, so you can burn a dozen boards testing opening guesses without spending the daily.