This puzzle consists completely of binary numbers, so all the characters needed to fill in the squares will be 0s or 1s. The crossword is a 4x4 square grid, so all numbers will be written in binary, with 4 digits; e.g., 1 will be 0001, 2 will be 0010, and 4, 0100. The NOT operation changes all 0s to 1's and all 1s to 0s; e.g., NOT(0110) is 1001 and NOT(1010) is 0101.

Rows:
1. "2 Down" x 2
2. A triangular number
3. The cube of ("4 Down" - 2)
4. "3 Across" + "3 Down"

Columns:
1. NOT "2 Across"
2. NOT "1 Across"
3. "2 Across" x 2
4. "4 Across" - "1 Across"