How to play

The grid uses three symbols: ▲, ■, and ●.

Every row, read left to right, must combine to the target symbol shown at its right edge.

Every column, read top to bottom, must combine to the target shown at its bottom.

How symbols combine

Use the small table next to the grid. The key things to remember:

■ + anything = anything (■ does nothing)

▲ + ▲ = ●

● + ● = ▲

▲ + ● = ■

The order doesn't matter — ▲ + ● is the same as ● + ▲.

The hidden target

One row or column has its target hidden — shown as a ? instead of a symbol. Tap it to cycle through your guess. You need to get this right too.

Playing

Tap a blank cell to cycle through symbols. Tap the small corner of any cell to leave yourself a private note. Press Check when you're ready. Correct rows and columns will turn green. You have three attempts.

A puzzle is solved when every blank is filled, the hidden target is right, and every row and column combines correctly.

If you're stuck

Combining a whole row

Take the row's symbols one at a time, left to right. For example:

▲ ● ■ ▲ ▲ = ?

First combine ▲ + ● = ■.
Then ■ + ■ = ■.
Then ■ + ▲ = ▲.
Then ▲ + ▲ = ●.

So this row resolves to ●.

Solving a blank cell

Blank cells are shown in a darker shade. Suppose this row needs to resolve to ●:

▲ ■ ? ● ▲ = ●

Combine the symbols you know, working around the blank:
▲ + ■ = ▲
● + ▲ = ■ (combining the two known symbols on the right)

So the row reduces to ▲ + ? + ■ = ●.
That means ? must be ▲, because ▲ + ▲ + ■ = ●.

Every blank sits in both a row and a column, so check both as you go.

This is one way to do it. Players find their own.