LongWords app for iPhone and iPad

On a 4x4 board, letters appear randomly. The goal of the game is to keep the board as free as possible, forming longer words. Letters of these words disappear on the board and accumulate points ($) based on the value of the letters. When you type a non-existent word but subtract the points. For a number of dollars, a follow-up word is suggested. You can also get paid by watching an ad with reward. Depending on the amount you accumulate, you can get to higher levels with a higher number of letters. The game ends when the board is filled and you can not find a sequel