Give examples of not independent random variables which are uniform s.t. $P(X+Y=1)=1$ and $X+Y$ which is uniform in the interval $[0,2]$

Question

Give examples of (not independent) random variables $X$ and $Y$, both of which are uniform in the interval $[0, 1]$ and such that

1. $\mathbb{P}(X + Y = 1) = 1$
2. $X + Y$ is uniform in the interval $[0, 2]$.

Answer 1

For 1. take $Y=1-X$. Prove that $Y$ is uniformly distributed.

For 2. Take $Y= \alpha X$. Prove that $X+Y = (1+\alpha) X$ is uniformly distributed on $[0,1+\alpha]$. For which $\alpha$ will $Y$ be uniform on the unit interval?