Why these three
Each one corresponds to something the puzzles here already lean on. The timer is the habit side of playing in short bursts rather than long ones. The matrix calculator is the arithmetic behind the 4×4 grid in 2048 — the game slides and merges a grid; this does the maths on one. The rhyme finder is the word-retrieval side of Wordle.
They are deliberately small. A tool that does one thing and does it correctly beats a page that pretends to do ten, and small pages load fast on a school network.