Find the theme words together. Drag through letters in any direction, including diagonals, or tap them one at a time and tap the last letter again to submit. The yellow spangram describes the theme and touches two opposite sides. Easy and Medium show each word's length below the board, and Easy gives you the first letters too. Every letter gets used. Words fill in the colour of whoever found them, and you can see each other's selection live. Same link on both phones puts you in the same room; add #something to the address for a private one.
You can switch any time from the top corner.