By Kevin Hwang, Sid Creutz, Rachel Bowens-Rubin, Tim Robertson, Ariel Schwartz
Answer: STUMBLE

Solvers are presented with two lists of clues, labeled Across and Down. The diagram is not given, but consists of a 9x18 grid with no black squares. The grid can be filled fairly simply, with the caveat that the across clues are numbered in reverse (such that 1 is the lowest row and 18 is the highest row). Filling in the clues provides the following filled grid:

A B C D E F G H I
18 C E L E S T I A L
17 A X I S M U N D I
16 V O S O U T P U T
15 E P A T S O H O T
14 O L D E U R O P E
13 F A I R S M E A R
12 B N A I H O B O S
11 E E G C I S E L W
10 A T R A G E D I E
9 S T A B O S O N S
8 T I M O R B A I T
7 S A U D I R U N G
6 S A N A D E L I E
5 U N I T E D A P R
4 I N T E R E N U M
3 T U O M I M O S A
2 U A V S L I V E N
1 P L A N E T A R Y

At this point, solvers will have a 9x18 grid, with the across numbers going from bottom to top. In addition, there are directional anchors presented along the outer edge of the grid: CELESTIAL and PLANETARY form the top and bottom of the grid, and EAST and WEST can be found on the left and right edges of the grid. This combined information should point solvers to the actual grid in question, which is the Green Building (building 54), specifically the North side of the building (from building 16/56). This is also hinted by the title (which hints “it’s not easy being green”).

A B C D E F G H I
18 C E L E S T I A L
17 A X I S M U N D I
16 V O S O U T P U T
15 E P A T S O H O T
14 O L D E U R O P E
13 F A I R S M E A R
12 B N A I H O B O S
11 E E G C I S E L W
10 A T R A G E D I E
9 S T A B O S O N S
8 T I M O R B A I T
7 S A U D I R U N G
6 S A N A D E L I E
5 U N I T E D A P R
4 I N T E R E N U M
3 T U O M I M O S A
2 U A V S L I V E N
1 P L A N E T A R Y

Solvers would now head towards the building itself to figure out in what way the building has been used. On the north side of the building, solvers would see the following (image taken from adjacent to building 16):

During Hunt, there was a blinking arrow in the window pointing down and to the right. If that clue is interpreted within the confines of the actual grid, the path spells the word STUMBLE, which is the answer to the puzzle.

A B C D E F G H I
18 C E L E S T I A L
17 A X I S M U N D I
16 V O S O U T P U T
15 E P A T S O H O T
14 O L D E U R O P E
13 F A I R S M E A R
12 B N A I H O B O S
11 E E G C I S E L W
10 A T R A G E D I E
9 S T A B O S O N S
8 T I M O R B A I T
7 S A U D I R U N G
6 S A N A D E L I E
5 U N I T E D A P R
4 I N T E R E N U M
3 T U O M I M O S A
2 U A V S L I V E N
1 P L A N E T A R Y