What is 1+1? Is it 2 or is it window?

it is this

We're no strangers to love

You know the rules and so do I

A full commitment's what I'm thinking of

You wouldn't get this from any other guy

I just wanna tell you how I'm feeling

Gotta make you understand

never gonna give you up

never gonna let you down

never gonna run around and desert you

never gonna make you cry

never gonna say goodbye

never gonna tell a lie and hurt you

We've known each other for so long

Your heart's been aching, but you're too shy to say it

Inside, we both know what's been going on

We know the game, and we're gonna play it

And if you ask me how I'm feeling

Don't tell me you're too blind to see

no not all of them.

step-by-step explanation:

some of them have a square base.