i-Memorize Sheet

Ranked #1 in Education (free) with over 1 million downloads, i-Memorize Sheet is a memorization study app that hides words and sentences using a red-filter effect, reproducing the feel of a real red sheet. You can import materials by converting them to PDF and study with just an iPhone.

Benefits include portable, one-handed study on the go, the ability to carry many pages, and check marks to track progress. It supports photos and PDFs, offers a free tier up to 10 pages, and an add-on to unlock more materials and remove ads.