Learn Hardcore Indonesian: Teman saya lebih tertarik membuat robot kecil yang bisa mengikuti garis di lantai. - My friend is more interested in making a small robot that can follow a line on the floor.

You almost never say *saya teman for “my friend”; that would sound wrong.
If you want an even more casual form, you might see temanku (-ku is a clitic form of aku), but the word order still keeps the noun first.

Where is the verb “is” in this sentence? Why don’t we need something like “Teman saya adalah lebih tertarik …”?

Indonesian usually does not use a separate verb like “is/are” (a copula) when the predicate is:

an adjective or adjective-like word, or
a verb phrase

In Teman saya lebih tertarik membuat…, the predicate is the phrase:

lebih tertarik membuat robot kecil yang…

So the structure is simply:

[subject] + [predicate]
Teman saya + lebih tertarik membuat…

You could add adalah before a noun phrase (“Teman saya adalah guru” = “My friend is a teacher”), but here, lebih tertarik membuat… isn’t a noun; it’s closer to “more interested in making…”, so you don’t use adalah.

What exactly does lebih tertarik mean, and do we always need lebih with tertarik?

tertarik = interested
lebih = more

So:

tertarik = (is) interested
lebih tertarik = (is) more interested

You don’t always need lebih. Compare:

Teman saya tertarik membuat robot.
My friend is interested in making a robot.
Teman saya lebih tertarik membuat robot.
My friend is more interested in making a robot (than in something else).

Often the “than X” part is understood from context and omitted, like here. Native speakers are comfortable leaving that comparison implicit.

Why is it lebih tertarik membuat and not lebih tertarik untuk membuat?

Both are possible:

Teman saya lebih tertarik membuat…
Teman saya lebih tertarik untuk membuat…

The meaning is the same: “more interested in making…”.

Differences:

Leaving out untuk is common and quite natural, especially in spoken or neutral Indonesian.
Adding untuk can sound a bit more explicit or careful, and is perfectly correct in both spoken and written language.

So:

tertarik + (untuk) + [verb]

is a normal pattern, and untuk is optional here.

What is the difference between membuat and buat?

Both come from the same root buat (“to make; to create”), but:

membuat
- is the standard meN- verb form
- more neutral and slightly more formal
- common in writing and careful speech
buat (bare root as a verb)
- is more informal / colloquial
- very common in casual conversation

In this sentence, membuat is the best choice, especially in written or neutral Indonesian:

Teman saya lebih tertarik membuat robot kecil…

In speech, some people might casually say:

Teman saya lebih tertarik buat robot kecil…

and it would still be understood as “to make a small robot”.

Why is it robot kecil and not kecil robot? Where do adjectives usually go?

In Indonesian, adjectives normally come after the noun:

robot kecil = small robot
rumah besar = big house
mobil baru = new car

So the pattern is:

[noun] + [adjective]

Saying *kecil robot is ungrammatical as a noun phrase.
The only time you might see something like “kecil, robot itu…” is if kecil is a separate predicate (“small, that robot is…”), not part of the noun phrase.

What does yang do in robot kecil yang bisa mengikuti garis di lantai?

yang introduces a relative clause (a clause that describes a noun), similar to “that/which/who” in English.

Breakdown:

robot kecil = small robot
yang bisa mengikuti garis di lantai = that can follow a line on the floor

So the full noun phrase is:

robot kecil yang bisa mengikuti garis di lantai
“a small robot that can follow a line on the floor”

Without yang, it would sound broken and confusing:

*robot kecil bisa mengikuti garis… → sounds like a full sentence “The small robot can follow a line…”, not a modifier of “robot”.

You generally must use yang to link a modifying clause to its noun.

Can I omit bisa and just say robot kecil yang mengikuti garis di lantai?

Yes, you can. The nuance changes slightly:

yang bisa mengikuti garis…
- “that can follow a line…” (focus on capability)
yang mengikuti garis…
- “that follows a line…” (more like describing what it does)

In context, both are natural. Including bisa emphasizes the robot’s ability; omitting it just states the action as a characteristic behavior. For describing a line-following robot, bisa mengikuti is very typical.

Does di lantai mean “on the floor” or “at the floor”? Why di and not pada?

For physical location, di is the normal preposition:

di lantai = on the floor / at the floor level
di meja = on the table
di dinding = on the wall

English sometimes uses “on” where Indonesian still uses di, so:

di lantai corresponds to on the floor in most contexts.

pada is more formal and is often used for:

abstract locations (“pada masa itu” = at that time)
certain fixed expressions
more formal/official language

Here, di lantai is the natural choice for everyday Indonesian.

What does mengikuti garis literally mean, and is garis the right word for a drawn line on the floor?

mengikuti = to follow (what comes after is the object)
garis = line (a drawn line, stripe, boundary, etc.)

So:

mengikuti garis = to follow a line

For a typical line-following robot that follows a painted/taped line on the floor, garis is exactly the normal word. If the line is a track, you might also see:

garis di lantai (line on the floor)
jalur di lantai (track/path on the floor)

But garis is standard and fully correct here.

Does the sentence need a classifier like sebuah before robot?

It’s optional:

membuat robot kecil…
membuat sebuah robot kecil…

Both are correct. Adding sebuah:

emphasizes that it’s one robot
sounds a bit more explicit or slightly more formal

Indonesian often omits classifiers and numbers when they’re not crucial. In this context, membuat robot kecil… already clearly implies “a small robot” without needing sebuah.

Why is the pronoun saya used instead of aku? Could we say Teman aku?

saya and aku both mean “I / me”, but differ in register:

saya
- more formal / neutral
- safe in almost all situations (talking to strangers, in writing, in class, at work)
aku
- informal / intimate
- often used with friends, family, people of the same age

So:

Teman saya = my friend (neutral, polite)
Teman aku = my friend (informal, casual)

Both are grammatically correct. In writing for learners or in neutral context, teman saya is generally preferred.