I simplified the library "ILI9225_TFT" provided by Arman Safikhani to better suit my needs in implementing a simple sliding puzzle game.

Revision:
3:251e4d020501
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Effects.h	Fri Apr 27 07:33:56 2018 +0000
@@ -0,0 +1,318 @@
+#include "ILI9225.h"
+#include <time.h>
+
+//Initialize pins for MBED LPC1768: RST, RS, CS, SDI(MOSI), CLK(SCK), LED.
+ILI9225 tft(P2_4, P2_3, P2_5, P0_9, P0_7, P0_6);
+DigitalOut led1(LED1);
+DigitalOut led2(LED2);
+DigitalOut led3(LED3);
+DigitalOut led4(LED4);
+
+//Initialize pins for LPCXPRESSO LPC1769: RST, RS, CS, SDI(MOSI), CLK(SCK), LED.
+//ILI9225 tft(P0_5, P0_10, P0_4, P0_18, P0_15, P0_16);
+
+//???b used out of 256kb available.
+//uint16_t picture[13986] = {0};
+
+uint16_t *picture = (uint16_t *)(0x2007C000);
+
+uint8_t puzzState[16] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
+    15};
+    
+uint8_t cursorIndex = 0; //Refers to current index (-1 < cursorIndex < 16).
+
+Timer timer; //Timer used to implement wireless input 
+InterruptIn wirelessInput(p18); //Interrupt used to implement wireless input
+float wirelessInput_Freq = 0; //Global variable used to implement wireless input
+
+void flip() {
+    //Convert period (in us) to frequency (Hz)
+    wirelessInput_Freq = (1/(float)timer.read_us())*1000000;
+    //Reset timer and wait for next interrupt
+    timer.reset();
+}
+
+int getPlayerInput(float freq) {
+    int specifier = (((int)freq) - (((int)freq)%1000))/1000;
+    wait_ms(1);
+    if(specifier == 1) {
+        //Turn on LED indicator(s): controller is in range.
+        led1 = led2 = led3 = led4 = 1;
+        return 0;
+    }
+    else if(specifier > 0 && specifier < 8) {
+        //Turn on LED indicator(s): controller is in range.
+        led1 = led2 = led3 = led4 = 1;
+        return specifier;
+    }
+    else {
+        //Turn off LED indicator(s): controller is NOT in range.
+        led1 = led2 = led3 = led4 = 0;
+        return 0;
+    }
+}
+
+void printNumber(int x, int y, uint8_t number) {
+    //tft.fillRectangle(0, 0, 175, 91, COLOR_BLACK);
+    tft.setFont(Terminal12x16);
+        
+    if(number == 0)
+        tft.drawText(x, y, "0", COLOR_WHITE);
+    else if(number == 1)
+        tft.drawText(x, y, "1", COLOR_WHITE);
+    else if(number == 2)
+        tft.drawText(x, y, "2", COLOR_WHITE);
+    else if(number == 3)
+        tft.drawText(x, y, "3", COLOR_WHITE);
+    else if(number == 4)
+        tft.drawText(x, y, "4", COLOR_WHITE);
+    else if(number == 5)
+        tft.drawText(x, y, "5", COLOR_WHITE);
+    else if(number == 6)
+        tft.drawText(x, y, "6", COLOR_WHITE);
+    else if(number == 7)
+        tft.drawText(x, y, "7", COLOR_WHITE);
+    else if(number == 8)
+        tft.drawText(x, y, "8", COLOR_WHITE);
+    else if(number == 9)
+        tft.drawText(x, y, "9", COLOR_WHITE);
+    else if(number == 10)
+        tft.drawText(x, y, "10", COLOR_WHITE);
+    else if(number == 11)
+        tft.drawText(x, y, "11", COLOR_WHITE);
+    else if(number == 12)
+        tft.drawText(x, y, "12", COLOR_WHITE);
+    else if(number == 13)
+        tft.drawText(x, y, "13", COLOR_WHITE);
+    else if(number == 14)
+        tft.drawText(x, y, "14", COLOR_WHITE);
+    else if(number == 15)
+        tft.drawText(x, y, "15", COLOR_WHITE);
+    else
+        tft.drawText(x, y, "?", COLOR_WHITE);
+}
+
+void printElementsInPicture() {
+    tft.fillRectangle(0, 0, 175, 91, COLOR_BLACK);
+    for(int i = 0; i < 16; i++)
+        printNumber((40*(i%4)) + 8, (20*((i - (i%4))/4)) + 8, puzzState[i]);
+}
+
+//Put contents of pictureN at target index on GLCD specified by 'index'.
+void printPictureN(int index, int N) {
+    int c = index%4;
+    int r = (index - c)/4;
+    
+    if(N > 13) {
+        tft.fillRectangle((39*c) + 11, (29*r) + 95,
+            (39*c) + 47, (29*r) + 121, COLOR_BLACK);
+        return;
+    }
+    for(int x = (39*c) + 11; x <= (39*c) + 47; x++) {
+        for(int y = (29*r) + 95; y <= (29*r) + 121; y++)
+            tft.drawPixel(x, y, picture[(999*N) + (4*y) + x]);
+    }
+}
+
+void updatePuzzle() {
+    for(int N = 0; N < 16; N++)
+        printPictureN(N, puzzState[N]);
+}
+
+int getNextPixel_index = 0;
+
+//**TODO** replace the contents of the following method with the code necessary
+//to get the next pixel from the OV7670. The method, in its current state, is
+//good for testing purposes. You should also be able to remove the
+//'getNextPixel_index' variable if you correctly implement this new method.
+uint16_t getNextPixel() {
+    uint16_t value = 0;
+    
+    int x, y;
+    
+    if(getNextPixel_index > 19199) {
+        getNextPixel_index = 0;
+        x = 0;
+    }
+    else
+        x = getNextPixel_index%160;
+    y = (getNextPixel_index - x)/160;
+    
+    //Is pixel in one of 4 outer pieces (corners)?
+    if((x >= 0 && x <= 40) && (y >= 0 && y <= 30)) //Upper left corner.
+        value = 65535;
+    if((x >= 119 && x <= 159) && (y >= 0 && y <= 30)) //Upper right corner.
+        value = 52428;
+    if((x >= 0 && x <= 40) && (y >= 89 && y <= 119)) //Lower left corner.
+        value = 13107;
+    if((x >= 119 && x <= 159) && (y >= 89 && y <= 119)) //Lower right corner.
+        value = 0;
+    
+    //Is pixel in one of 4 outer pieces (left and right)?
+    if((x >= 0 && x <= 40) && (y >= 31 && y <= 59)) //Upper left side.
+        value = 48059;
+    if((x >= 0 && x <= 40) && (y >= 60 && y <= 88)) //Lower left side.
+        value = 30583;
+    if((x >= 119 && x <= 159) && (y >= 31 && y <= 59)) //Upper right side.
+        value = 34952;
+    if((x >= 119 && x <= 159) && (y >= 60 && y <= 88)) //Lower right side.
+        value = 17476;
+    
+    //Is pixel in one of 4 outer pieces (top and bottom)?
+    if((x >= 41 && x <= 79) && (y >= 0 && y <= 30)) //Left top side.
+        value = 61166;
+    if((x >= 80 && x <= 118) && (y >= 0 && y <= 30)) //Right top side.
+        value = 56797;
+    if((x >= 41 && x <= 79) && (y >= 89 && y <= 119)) //Left bottom side.
+        value = 8738;
+    if((x >= 80 && x <= 118) && (y >= 89 && y <= 119)) //Right bottom side.
+        value = 0;
+    
+    //Is pixel in one of 4 inner pieces?
+    if((x >= 41 && x <= 79) && (y >= 31 && y <= 59)) //Upper left inner piece.
+        value = 43690;
+    if((x >= 80 && x <= 118) && (y >= 31 && y <= 59)) //Upper right inner piece.
+        value = 39321;
+    if((x >= 41 && x <= 79) && (y >= 60 && y <= 88)) //Lower left inner piece.
+        value = 26214;
+    if((x >= 80 && x <= 118) && (y >= 60 && y <= 88)) //Lower right inner piece.
+        value = 21845;
+    
+    getNextPixel_index++;
+    
+    return value;
+}
+
+void handlePixel(int index, uint16_t pixel) {
+    int x = index%160;
+    int y = (index - x)/160;
+    if((x >= 3 && x <= 39) && (y >= 3 && y <= 29))
+        picture[37*y + x - 114] = pixel;
+    else if((x >= 42 && x <= 78) && (y >= 3 && y <= 29))
+        picture[37*y + x - 153 + 999] = pixel;
+    else if((x >= 81 && x <= 117) && (y >= 3 && y <= 29))
+        picture[37*y + x - 192 + 1998] = pixel;
+    else if((x >= 120 && x <= 156) && (y >= 3 && y <= 29))
+        picture[37*y + x - 231 + 2997] = pixel;
+    else if((x >= 3 && x <= 39) && (y >= 32 && y <= 58))
+        picture[37*y + x - 1187 + 3996] = pixel;
+    else if((x >= 42 && x <= 78) && (y >= 32 && y <= 58))
+        picture[37*y + x - 1226 + 4995] = pixel;
+    else if((x >= 81 && x <= 117) && (y >= 32 && y <= 58))
+        picture[37*y + x - 1265 + 5994] = pixel;
+    else if((x >= 120 && x <= 156) && (y >= 32 && y <= 58))
+        picture[37*y + x - 1304 + 6993] = pixel;
+    else if((x >= 3 && x <= 39) && (y >= 61 && y <= 87))
+        picture[37*y + x - 2260 + 7992] = pixel;
+    else if((x >= 42 && x <= 78) && (y >= 61 && y <= 87))
+        picture[37*y + x - 2299 + 8991] = pixel;
+    else if((x >= 81 && x <= 117) && (y >= 61 && y <= 87))
+        picture[37*y + x - 2338 + 9990] = pixel;
+    else if((x >= 120 && x <= 156) && (y >= 61 && y <= 87))
+        picture[37*y + x - 2377 + 10989] = pixel;
+    else if((x >= 3 && x <= 39) && (y >= 90 && y <= 116))
+        picture[37*y + x - 3333 + 11988] = pixel;
+    else if((x >= 42 && x <= 78) && (y >= 90 && y <= 116))
+        picture[37*y + x - 3372 + 12987] = pixel;
+}
+
+//A utility function to swap 2 numbers
+void swap(uint8_t *a, uint8_t *b) {
+    uint8_t temp = *a;
+    *a = *b;
+    *b = temp;
+}
+
+void shuffleGridIndices() {
+    int n = sizeof(puzzState)/sizeof(puzzState[0]);
+    
+    //Use a different seed value so that we don't get same result each time we
+    //run this program.
+    srand(time(NULL));
+ 
+    //Start from the last element and swap one by one. We don't need to run for
+    //the first element, which is why i > 0.
+    for (int i = n-1; i > 0; i--) {
+        int j = rand()%(i+1); //Pick a random index b.w. 0 & i.
+        swap(&puzzState[i], &puzzState[j]); //Swap w| element @ random index.
+    }
+}
+
+//This method puts a picture on the screen that is/was helpful during testing.
+void putTestPicture() {
+    //Add 4 outer pieces (corners).
+    tft.fillRectangle(8, 92, 48, 122, 65535); //Upper left corner.
+    tft.fillRectangle(127, 92, 167, 122, 52428); //Upper right corner.
+    tft.fillRectangle(8, 181, 48, 211, 13107); //Lower left corner.
+    tft.fillRectangle(127, 181, 167, 211, 0); //Lower right corner.
+    
+    //Add 4 outer pieces (left and right).
+    tft.fillRectangle(8, 123, 48, 151, 48059); //Upper left side.
+    tft.fillRectangle(8, 152, 48, 180, 30583); //Lower left side.
+    tft.fillRectangle(127, 123, 167, 151, 34952); //Upper right side.
+    tft.fillRectangle(127, 152, 167, 180, 17476); //Lower right side.
+    
+    //Add 4 outer pieces (top and bottom).
+    tft.fillRectangle(49, 92, 87, 122, 61166); //Left top side.
+    tft.fillRectangle(88, 92, 126, 122, 56797); //Right top side.
+    tft.fillRectangle(49, 181, 87, 211, 8738); //Left bottom side.
+    tft.fillRectangle(88, 181, 126, 211, 0); //Right bottom side.
+    
+    //Add 4 inner pieces.
+    tft.fillRectangle(49, 123, 87, 151, 43690); //Upper left inner piece.
+    tft.fillRectangle(88, 123, 126, 151, 39321); //Upper right inner piece.
+    tft.fillRectangle(49, 152, 87, 180, 26214); //Lower left inner piece.
+    tft.fillRectangle(88, 152, 126, 180, 21845); //Lower right inner piece.
+}
+
+void putGrid() {
+    tft.drawRectangle(8, 92, 167, 211, COLOR_WHITE);
+    tft.drawRectangle(9, 93, 166, 210, COLOR_WHITE);
+    
+    for(int r = 0; r < 4; r++) {
+        for(int c = 0; c < 4; c++)
+            tft.drawRectangle(39*c + 10, 29*r + 94, 39*c + 48, 29*r + 122,
+                COLOR_WHITE);
+    }
+}
+
+void highlightGridIndex(uint8_t index, bool hasSelected) {
+    int c = index%4;
+    int r = (index - c)/4;
+    putGrid();
+    if(hasSelected) //Red highlight means player has selected an index.
+        tft.drawRectangle(39*c + 10, 29*r + 94, 39*c + 48, 29*r + 122,
+            COLOR_RED);
+    if(!hasSelected) //Green highlight means player has not selected an index.
+        tft.drawRectangle(39*c + 10, 29*r + 94, 39*c + 48, 29*r + 122,
+            COLOR_GREEN);
+    cursorIndex = index;
+}
+
+bool selectionMode_indexVerified(uint8_t index) {
+    //index must satisfy 2 characteristics for method to return true.
+
+    //1) Target puzzle piece is NOT one of the 2 missing puzzle pieces.
+    if(puzzState[index] > 13)
+        return false;
+    
+    //2) Target puzzle piece is NOT locked on all 4 sides.
+    if(index - 4 > -1) { //NOT out of bounds above.
+        if(puzzState[index - 4] > 13) //Empty space above?
+            return true;
+    }
+    if(index + 4 < 16) { //NOT out of bounds below.
+        if(puzzState[index + 4] > 13) //Empty space below?
+            return true;
+    }
+    if((index%4) - 1 > -1) { //NOT out of bounds to the left.
+        if(puzzState[index - 1] > 13) //Empty space to the left?
+            return true;
+    }
+    if((index%4) + 1 < 4) { //NOT out of bounds to the right.
+        if(puzzState[index + 1] > 13) //Empty space to the right?
+            return true;
+    }
+
+    return false;
+}
\ No newline at end of file