I can see why you may think it will decrease accuracy, however, even if the buttons get larger, the way the user aims his finger should stay the same. This will increase usability and allow more users to use you're excellent calculator without needing to reach for a stylus!
If it would make it easier, I can prepare all of the rectangle coordinates. I would only need the number of units width and height of the skin (lets try ATI86) and I'll do the rest!
/** TouchMap[] ***********************************************/ /** This map translates on-screen rectangles into keys. **/ /*************************************************************/ struct { byte KeyCode; int X,Y,W,H; } TouchMap[] = { { KBD_RIGHT, 380,45,43,28 }, { KBD_LEFT, 380,163,43,28 }, { KBD_UP, 352,89,25,58 }, { KBD_DOWN, 427,89,25,58 }, { KBD_F5, 291,43,25,65 }, { KBD_F4, 291,125,25,65 }, { KBD_F3, 291,207,25,65 }, { KBD_F2, 291,289,25,65 }, { KBD_F1, 291,371,25,65 }, { KBD_CLEAR, 467,40,30,67 }, { KBD_POWER, 511,40,30,67 }, { KBD_DIV,555,40,30,67 }, { KBD_MUL, 599,40,30,67 }, { KBD_MINUS, 643,40,30,67 }, { KBD_PLUS, 687,40,30,67 }, { KBD_ENTER, 731,40,38,67 }, { KBD_CUSTOM, 467,123,30,67 }, { KBD_TAN, 511,123,30,67 }, { KBD_RPARENT,555,123,30,67 }, { KBD_9, 599,123,30,67 }, { KBD_6, 643,123,30,67 }, { KBD_3, 687,123,30,67 }, { KBD_SIGN, 731,123,30,67 }, { KBD_MORE, 379,206,30,67 }, { KBD_DEL, 423,206,30,67 }, { KBD_PRGM, 467,206,30,67 }, { KBD_COS, 511,206,30,67 }, { KBD_LPARENT,555,206,30,67 }, { KBD_8, 599,206,30,67 }, { KBD_5, 643,206,30,67 }, { KBD_2, 687,206,30,67 }, { KBD_DOT, 731,206,30,67 }, { KBD_EXIT, 379,289,30,67 }, { KBD_XVAR, 423,289,30,67 }, { KBD_STAT, 467,289,30,67 }, { KBD_SIN, 511,289,30,67 }, { KBD_EE, 555,289,30,67 }, { KBD_7, 599,289,30,67 }, { KBD_4, 643,289,30,67 }, { KBD_1, 687,289,30,67 }, { KBD_0, 731,289,30,67 }, { KBD_2ND, 379,372,30,67 }, { KBD_ALPHA, 423,372,30,67 }, { KBD_GRAPH, 467,372,30,67 }, { KBD_LOG, 511,372,30,67 }, { KBD_LN, 555,372,30,67 }, { KBD_SQR, 599,372,30,67 }, { KBD_COMMA, 643,372,30,67 }, { KBD_STO, 687,372,30,67 }, { KBD_ON, 731,372,30,67 }, { 0,0,0,0,0 } };