Bluno: error: 'Serial' was not declared in this scope

Hi!

I am new to Arduino, and I am trying to run a very simple code on Bluno.

I use Macbook with Arduino IDE, and connect the Bluno via USB. I can tell that it is somewhat working, as the 'Blink' example works for me.

However, if I try using any of the Serial commands, I get the following error:
example:31: error: 'Serial' was not declared in this scope
if (Serial.available())
^

Is there anything I need to include to make this work?

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I found out that if I use SerialX for X in {1, 2, 3, 4, 5}, it uploads without errors. However, all calls to SerialX.available() return false.