Questions & Answers about Круто, ты всё сделал сам.
Круто is a very common informal reaction meaning Cool, Awesome, Great, or Nice.
In this sentence, it stands on its own as a comment on what the other person did:
- Круто = That’s cool / Nice / Awesome
It is conversational and natural in everyday speech.
The comma separates Круто from the rest of the sentence because Круто works like a separate reaction or exclamation.
So the structure is basically:
- Круто, = Cool,
- ты всё сделал сам = you did everything yourself
In speech, there is usually a pause after Круто. You could also see stronger punctuation in real life, such as:
- Круто! Ты всё сделал сам.
But with a comma, it still sounds very natural.