Along the bottom of the screen will be the alphabet. Touching on a letter will select it and it will be shown in the central area above the alphabet. Thus 3 letters "b", "a" and "d" might be selected. The user could continue selecting more letters or, at any time, they can start the game by pressing the "go" icon. Pressing the "go" icon will trigger the app to create a square grid containing random letters in which words made up of the selected letters are interspersed. For present purposes it makes sense to assume that the app contains a suitable file of age appropriate words and only words contained in that file will be used. That file will be supplied to the coder in whatever format they require.
The user then touches squares to highlight those squares which contain the words. Every square can be highlighted by direct touch and incorrectly highlighted squares can be "unhighlighted" or deselected by touching them again.
Eventually when the user is satisfied that they have found all the words they can press the reset button (the arrow icon) and begin another game. On pressing the reset button the grid and the selected letters will disappear and the central area will be clear ready for new letters to be chosen