Spelling practice on the same patterns the school schemes use, year by year. Every try is remembered on this device, so the words that still wobble come back until they don't. Works with no signal at all.
Same sound, different spelling and meaning. Learn them in pairs.
accept · except · affect · effect · piece…
The prefix changes shape to match the root: in + possible → impossible.
incorrect · invisible · impossible · impatient · illegal…