Learn Hardcore Spanish (Spain): No hace falta que compres más cereal; todavía queda en la caja. - You do not need to buy more cereal; there is still some left in the box.

No hace falta que compres más cereal = There’s no need for you to buy more cereal
No necesitas comprar más cereal = You don’t need to buy more cereal

The difference is mostly one of style and focus:

No hace falta que... sounds a bit more impersonal and general.
No necesitas... speaks more directly to the person.

Both are common and correct.

Why is there a que after no hace falta?

Because que introduces the following clause: compres más cereal.

This is very common in Spanish. Many expressions are followed by que + verb:

Es importante que estudies
Quiero que vengas
No hace falta que compres más cereal

So here, que is not optional. You need it before the subjunctive verb.

Why is it más cereal and not más cereales?

Here, cereal is being used as an uncountable or mass noun, like bread or rice in English.

So más cereal means more cereal as a quantity of food, not more kinds of cereals.

This is very natural in Spanish:

Queda cereal
Compra más cereal
No queda leche

You might see cereales in other contexts, especially when talking about breakfast cereals as products or types, but in this sentence cereal as a mass noun is perfectly normal.

Why is it queda and not quedan?

Because the thing that remains is understood as cereal, which is singular here.

Todavía queda en la caja = There is still some left in the box

The verb quedar agrees with the thing left over:

Queda cereal = There is cereal left
Quedan galletas = There are biscuits/cookies left

Since cereal is treated as singular and uncountable in this sentence, Spanish uses queda.

What does todavía mean, and could aún be used instead?

Todavía means still.

So:

todavía queda en la caja = there’s still some left in the box

Yes, aún could also be used here:

Aún queda en la caja

In many contexts, todavía and aún mean the same thing. Todavía is often a little more common in everyday speech, but both are correct.

What does en la caja mean exactly?

It means in the box.

In this context, it refers to the cereal container, so the idea is:

there is still some cereal left in the box/package

In everyday Spanish, caja is a normal word for a box of cereal. Depending on the product and packaging, other words may also be possible in other contexts, but la caja sounds completely natural here.

Why doesn’t Spanish repeat the noun after queda?

Because Spanish often leaves out words that are easy to understand from context.

The full idea is something like:

Todavía queda cereal en la caja

But once cereal has already been mentioned, Spanish can simply say:

Todavía queda en la caja

This is very natural. English does something similar:

There’s still some left in the box

So the noun is omitted because it is obvious what is being talked about.

Can I add tú and say No hace falta que tú compres más cereal?

Yes, grammatically you can, but normally you would not include tú unless you want emphasis or contrast.

Spanish usually leaves subject pronouns out because the verb already shows the person:

compres already tells us it is you singular

So the neutral version is:

No hace falta que compres más cereal

You might add tú only for emphasis, for example:

No hace falta que tú compres más cereal; yo lo compro.

That sounds like You don’t need to buy more cereal; I’ll buy it.

Why is there a semicolon in the sentence? Could it be a comma or a full stop?

Yes. The semicolon links two closely related ideas:

No hace falta que compres más cereal
todavía queda en la caja

It shows that the second part explains the first.

In everyday writing, a full stop would also be very natural:

No hace falta que compres más cereal. Todavía queda en la caja.

A comma is also possible in informal writing, although the semicolon or full stop is usually clearer.

Is quedar a common way to say to be left/remain?

Yes, very common.

In this sentence, quedar means to remain / to be left over:

Queda pan = There’s bread left
No queda leche = There’s no milk left
Todavía queda en la caja = There’s still some left in the box

This is one of the most useful everyday meanings of quedar, so it is worth learning well.