Oops! Angry Birds Star Wars Cloud City level 4-20 seems to feature some additional obstacles… Anyway, to make it to the 3-star achievement, fling Han Solo at a typical trajectory (through the steam generator), firing onto the black control panel that operates the barriers, getting your Bird through (while smashing the Storm Troopers positioned on the second barrier), popping onto the steam source and just managing to get across the second hindrance, hopefully creating a gap for the next Bird. For the next move, no opening switch will be needed, as Princess Leia (after being released onto the steam source) should get through the gap and, right before hitting the third closed barrier, use her tractor beam to pull up the planks, knocking down everything on that sector! Finally, fling Obi-Wan in a similar way as the previous Bird (onto the steam) and, right before he hits the lower of the two hanging blocks, activate his Force to push it directly onto Vader and his guarding Death Star Troopers, eliminating them, while also pulling the other block straight onto the leftover Storm Trooper! Well done!