In That Old Wallpaper you try to restore the wall of a house with wallpaper, matching as many patterns as possible.
There are a number of locations available in the game where wallpaper cards are up for grabs. Each turn, players simultaneously choose a location, and if you are the only one who chooses a location, you receive the card or cards at that location. If you choose the same location as someone else, everyone will receive a "blurry memory card" with a wallpaper pattern along only one edge instead of all four edges.
If you receive regular wallpaper cards, you should immediately add them to your other played cards, ideally matching the pattern halves to create a complete pattern. Patterns come in four colors, with each color having two sizes. There is also a joker pattern available, which seems a bit strange, but so be it. To end a turn, you deal a new wallpaper card to each location, which means some locations will likely have more cards than others.
At the end of the game, use your blurry memory cards to complete patterns on the edge of your wallpaper, then score for each color of the pattern. A pattern's score is the number of large symbols of that color multiplied by the number of small symbols, so if you don't have at least one large and small symbol, you won't score anything for that color!