Retrocede una casilla.

It is the affirmative tú command of retroceder.

• retroceder = to move back / to go back
• retrocede = move back / go back / back up

This is the command form you use when speaking directly to one person in an informal way.

Examples:

• Retrocede una casilla. = Move back one space.
• Avanza dos casillas. = Move forward two spaces.

Because retroceder is the infinitive form, meaning to move back or to go back. In this sentence, you are telling someone to do it, so Spanish uses a command form.

Compare:

• retroceder = to move back
• retrocede = move back! / go back!

So Retrocede una casilla is an instruction, like something you might read in a board game.

Spanish often omits subject pronouns when they are understood from the verb form.

So instead of saying:

• Tú retrocede una casilla

Spanish normally just says:

• Retrocede una casilla

The verb already tells you the sentence is directed at tú.

Including tú is possible, but it usually adds emphasis and is not necessary in a normal instruction.

Casilla usually means a space, square, or slot, depending on context.

In Retrocede una casilla, it most naturally means a space on a board game.

So if you are playing a game, una casilla is one position on the board.

Related words:

• casa = house
• casilla literally comes from a diminutive form, but in modern usage it often means a small square/space/box

Common contexts:

• board games: casilla
• forms/checklists: a box to mark
• chessboard/grid-like layouts: a square

Because Spanish normally uses an article or number here to show how many spaces.

• una casilla = one space
• dos casillas = two spaces
• tres casillas = three spaces

In game instructions, saying Retrocede una casilla is the natural way to express Move back one space.

Without una, the phrase would sound incomplete in this context.

It is informal, because retrocede is the tú command.

If you wanted the usted command, it would be:

• Retroceda una casilla.

So:

• retrocede = informal singular command
• retroceda = formal singular command

In board games and general instructions, Spanish often uses forms like this depending on tone and audience.

By itself, retrocede una casilla could also match the él/ella/usted present tense form:

• él retrocede = he moves back
• ella retrocede = she moves back
• usted retrocede = you move back (formal, indicative)

But context usually makes the meaning clear.

In a game, card, app, or instruction list, it is naturally understood as a command:

• Retrocede una casilla. = Move back one space.

If it were a normal statement, you would usually have more context or a subject:

• El jugador retrocede una casilla. = The player moves back one space.

A simple Latin American-style approximation is:

• reh-troh-SEH-deh OO-nah kah-SEE-yah

A few pronunciation notes:

• r in retrocede is a light tap at the beginning of the syllable
• c before e in Latin America is usually like English s
  • so retrocede sounds roughly like reh-troh-SEH-deh
• ll in many parts of Latin America sounds like y
  • so casilla often sounds like kah-SEE-yah

The natural stress is:

• retroCEde
• caSIlla

Retroceder is correct and quite common, especially in:

• instructions
• games
• signs
• formal or neutral contexts

But in everyday speech, people might also use more conversational expressions depending on the situation, such as:

• ve hacia atrás = go backward
• da un paso atrás = take a step back
• vuelve atrás = go back

For a board game or written instruction, Retrocede una casilla sounds very natural.

That depends on the variety of Spanish.

In most of Latin America, for you all, you would use ustedes:

• Retrocedan una casilla.

If speaking to one person formally:

• Retroceda una casilla.

If speaking to one person informally:

• Retrocede una casilla.

So the forms are:

• tú → retrocede
• usted → retroceda
• ustedes → retrocedan

Sometimes yes, but casilla is more natural for a board game or any layout made of distinct spaces/squares.

Compare:

• Retrocede una casilla. = the most natural for a game board
• Retrocede un espacio. = understandable, but less idiomatic in many game contexts

So a learner should recognize that casilla is a very useful word for board-game instructions and other square/boxed positions.