Here's why this is casual:
* Informal greetings: "Hey" is much more casual than "Hello" or "Good evening."
* Contractions: "Wanna" is a casual contraction of "want to."
* Simple vocabulary: The language is straightforward and avoids overly formal words.
* Informal tone: The sentence suggests a relaxed, friendly interaction.
Here's an example of more formal language to contrast:
"Would you be interested in joining me for a meal at a pizzeria this evening?"