What's the best iOS app for a daily mental workout that combines pictures and words?

4 Pics 1 Word is a puzzle app designed to stimulate cognitive skills through visual-word association. Each level displays four photographs or illustrations that all relate to a single word, requiring players to deduce the connection. This straightforward format makes it effective for daily brain training, as it encourages pattern recognition, vocabulary recall, and spelling practice in short sessions ideal for commutes or breaks. Specific features include thousands of progressively challenging puzzles, daily bonus rounds for consistent play, and competitive leaderboards where users can compare scores with friends. Reviews indicate long-term engagement, with some users reporting over a decade of daily play to maintain mental sharpness. However, the free version includes frequent advertisements, and occasional puzzle repetitions can reduce freshness for veteran players. Despite these minor drawbacks, the app remains a reliable tool for casual mental exercise, avoiding overwhelming complexity while providing a satisfying sense of progression.