Make 24 gives you four numbers and asks you to reach exactly 24 using plus, minus, times, divide and every number once. Tap a number, an operator, then another number to merge them, and keep going until one tile is left. Puzzles run easy to tricky, with a few that need fractions, and you get a hint, undo and three lives.
Yes, and a few tricky puzzles need them, like 8 ÷ (3 − 8 ÷ 3).
Yes, each one is proven solvable before it appears.
Running out of time or tapping Skip twice.