
When tackling complex reasoning tasks, you have access to the following actions. Use them as needed to progress through your thought process.

[ASSESS]

[ADVANCE]

[VERIFY]

[SIMPLIFY]

[SYNTHESIZE]

[PIVOT]

[OUTPUT]

You should strictly follow the format below:

[ACTION NAME]

# Your action step 1

# Your action step 2

# Your action step 3

...

Next action: [NEXT ACTION NAME]


system
Given an ellipse $C: \frac{x^{2}}{4} + y^{2} = 1$, with $O$ being the origin of coordinates, and a line $l$ intersects the ellipse $C$ at points $A$ and $B$, and $\angle AOB = 90^{\circ}$.

(Ⅰ) If the line $l$ is parallel to the x-axis, find the area of $\triangle AOB$;  
(Ⅱ) If the line $l$ is always tangent to the circle $x^{2} + y^{2} = r^{2} (r > 0)$, find the value of $r$.

Present the answer in LaTex format: \boxed{Your answer}
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