Не могу понять как работает программа и движок.

package com.javarush.games.game2048; import com.javarush.engine.cell.*; import java.util.Arrays; public class Game2048 extends Game { private static final int SIDE = 4; private int[][] gameField = new int[SIDE][SIDE]; public void initialize() { setScreenSize(SIDE, SIDE); createGame(); drawScene(); } private void createGame() { createNewNumber(); createNewNumber(); } private void drawScene() { for (int i = 0; i < SIDE; i++) { for (int j = 0; j < SIDE; j++) { setCellColoredNumber(j, i, gameField[i][j]); } } } private void createNewNumber() { while (true) { int x = getRandomNumber(SIDE); int y = getRandomNumber(SIDE); if (gameField[y][x] == 0) { int tmp = getRandomNumber(10); gameField[y][x] = tmp == 9 ? 4 : 2; break; } else continue; } } private void setCellColoredNumber(int x, int y, int value) { Color color = getColorByValue(value); String str = value > 0 ? "" + value : ""; setCellValueEx(x, y, color, str); } private Color getColorByValue(int value) { if (value == 0) return Color.WHITE; else if (value == 2) return Color.YELLOW; else if (value == 4) return Color.ORANGE; else if (value == 8) return Color.LIGHTPINK; else if (value == 16) return Color.DEEPPINK; else if (value == 32) return Color.RED; else if (value == 64) return Color.DARKRED; else if (value == 128) return Color.BLUE; else if (value == 256) return Color.DARKBLUE; else if (value == 512) return Color.LIMEGREEN; else if (value == 1024) return Color.DARKGREEN; else return Color.CORAL; } private boolean compressRow(int[] row) { int zero = 0; boolean result = false; for (int x = 0; x < SIDE; x++) { if (row[x] > 0) { if (x != zero) { row[zero] = row[x]; row[x] = 0; result = true; } zero++; } } return result; } private boolean mergeRow(int[] row) { boolean result = false; if (row[0] == row[1] && row[0] != 0) { row[0] = row[0] + row[1]; row[1] = 0; result = true; } if (row[1] == row[2] && row[1] != 0) { row[1] = row[1] + row[2]; row[2] = 0; result = true; } if (row[2] == row[3] && row[2] != 0) { row[2] = row[2] + row[3]; row[3] = 0; result = true; } return result; } public void onKeyPress(Key key) { if (key == Key.LEFT) { moveLeft(); drawScene(); } if (key == Key.RIGHT) { moveRight(); drawScene(); } if (key == Key.UP) { moveUp(); drawScene(); } if (key == Key.DOWN) { moveDown(); drawScene(); } } private void moveLeft() { int count = 0; boolean change = false; for (int[] row : gameField) { if (compressRow(row)) change = true; if (mergeRow(row)) change = true; if (compressRow(row)) change = true; } if (change) { createNewNumber(); } } private void moveRight() { rotateClockwise(); rotateClockwise(); moveLeft(); rotateClockwise(); rotateClockwise(); } private void moveUp() { rotateClockwise(); rotateClockwise(); rotateClockwise(); moveLeft(); rotateClockwise(); } private void moveDown() { rotateClockwise(); moveLeft(); rotateClockwise(); rotateClockwise(); rotateClockwise(); } private void rotateClockwise() { int[][] original = new int[SIDE][SIDE]; for (int i = 0; i < SIDE; i++) { for (int j = 0; j < SIDE; j++) { original[j][SIDE - 1 - i] = gameField[i][j]; } } gameField = original; } }