We have a lot to get through and in this article we are going to now start moving away from the nitty gritty line be line explanations as hopefully you are becoming more competent in game coding by now. I will outline the changes, present the code and, apart from highlighting any specifics, we will leave it at that. You are free to examine the code to see how the latest instalment was implemented. This should also mean we’ll get through more content from now on with more frequent articles.
Changes in this release
- You can now die if an Invader’s bomb hits you (but not by any other means yet).
- Lives will be decremented and if it gets to zero then it’s game over
- An attract screen
- Congratulations screen for beating high score
- Reset of high score
- Invader and level difficulty, i.e. Invaders move faster the less of them there are and the start lower down per level.
A video covering these changes is available as well as this article, see below:
Highlights – difficulty
As in the arcade game the invaders speed increases as less of them are on screen. Famously this was not an intended game mechanic (i.e. not in any intentional design) but was a by-product of the speed of the available processor at the time. When there were a lot of Invaders to move on screen it took time to plot them to screen. But as their numbers declined the processor didn’t have to plot as many so wasn’t working quite so hard, meaning it could get round to moving and plotting those that were left much sooner than normal – hence they moved faster. This proved an excellent difficulty factor during any one level.
We have very fast processors (compared to the late 70’s early 80’s) and as such we have to deliberately code speeding up. The code that handles this is in the routine MissileAndAlienCollisions. Its in this routine as this is where an Invader would be destroyed and thus they would be slightly less. Here’s the code extract:
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// calc new speed of aliens, note (float) must be before TOTAL_ALIENS to force float calc else // you will get an incorrect result Player.AlienSpeed=((1-(Player.AliensDestroyed/(float)TOTAL_ALIENS))*INVADERS_SPEED); // for very last alien make to fast! if(Player.AliensDestroyed==TOTAL_ALIENS-2) if(AlienXMoveAmount>0) AlienXMoveAmount=ALIEN_X_MOVE_AMOUNT*2; else AlienXMoveAmount=-(ALIEN_X_MOVE_AMOUNT*2); // for very last alien make to super fast! if(Player.AliensDestroyed==TOTAL_ALIENS-1) if(AlienXMoveAmount>0) AlienXMoveAmount=ALIEN_X_MOVE_AMOUNT*4; else AlienXMoveAmount=-(ALIEN_X_MOVE_AMOUNT*4); |
We have a general speed calculation for most of the game (line 584) but then some specific code where we get to the last couple where we increase the speed dramatically.
Level Difficulty
In addition (an intended designed in game mechanic) was that for every level the Invaders would start a little lower down, up until a certain level (perhaps level 4 I cannot remember at time of writing). Then the start height position would revert to the level 1 screen increasing as the levels progressed again until another four levels had passed etc. etc. In this way Space Invaders as no real designed end as such. The code in the NextLevel routine handles this, here’s the extract:
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YStart=((Player->Level-1) % LEVEL_TO_RESET_TO_START_HEIGHT)*AMOUNT_TO_DROP_BY_PER_LEVEL; |
Looks complex perhaps but all it’s doing is setting the Invaders Y start position per level. The Amount to drop per level is defined in the constant AMOUNT_TO_DROP_BY_PER_LEVEL. 4 pixels seems about right for this screen. In essence all we need to do is multiply the level number by this amount to get the Y position. However that would make the game technically impossible for higher level numbers as it could result with the Invaders starting on top of the players tank! So ( as it did in the original) we do this on a repeating cycle of levels. i.e. levels 1-4 they come down more and more then they reset back to the start for level 5 getting lower and lower again etc. etc. The part that accomplishes this is this:
((Player->Level-1) % LEVEL_TO_RESET_TO_START_HEIGHT+1)
The constant LEVEL_TO_RESET_TO_START_HEIGHT contains the level that we reset the Y start position back to the top. In this case I chose level 5. So the Invaders get lower and lower for levels 1 to 4 and start again at the top for level 5 etc. But how is this achieved? Well it’s all in the % (percentage). This is the modulus operator. It’s purpose is to return the remainder of an integer division. i.e. of I divide 4 by 3, then 3 would go in once and 1 would be left over, so 4 % 3 would give me 1 as the answer.
So in our code we divide the current level by 4 and then multiply this remainder by the amount to move down per level to get the Y Position for the Invaders. Look at this table of examples.
| Player Level | Player level -1 | LEVEL_TO_RESET_TO_START_HEIGHT | Remainder of : (Player level-1) % LEVEL_TO_RESET_TO_START_HEIGHT | Multiply remainder by AMOUNT_TO_DROP_BY_PER_LEVEL to get Y Position |
|---|---|---|---|---|
| 1 | 0 | 4 | 0 | 0 |
| 2 | 1 | 4 | 1 | 4 |
| 3 | 2 | 4 | 2 | 8 |
| 4 | 3 | 4 | 3 | 12 |
| 5 | 4 | 4 | 0 | 0 |
| 6 | 5 | 4 | 1 | 4 |
| 7 | 6 | 4 | 2 | 8 |
Resetting the high score
If you wish to reset the high score it is implemented by pressing both the left and right buttons at once when on the attract screen. If you look back at previous articles and code it was originally intended to have it’s own button but at the last minute I’ve decided to reduce the button count and do it this way instead.
That’s it for this article, all that remains is to list the full source code for you to paste into your current Invaders project,
Enjoy 🙂
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#include <Adafruit_SSD1306.h> #include <Adafruit_GFX.h> #include <EEPROM.h> // DISPLAY SETTINGS #define OLED_ADDRESS 0x3C #define SCREEN_WIDTH 128 #define SCREEN_HEIGHT 64 // Input settings #define FIRE_BUT 6 #define RIGHT_BUT 5 #define LEFT_BUT 4 // Mothership #define MOTHERSHIP_HEIGHT 4 #define MOTHERSHIP_WIDTH 16 #define MOTHERSHIP_SPEED 2 #define MOTHERSHIP_SPAWN_CHANCE 250 //HIGHER IS LESS CHANCE OF SPAWN #define DISPLAY_MOTHERSHIP_BONUS_TIME 20 // how long bonus stays on screen for displaying mothership // Alien Settings #define ALIEN_HEIGHT 8 #define NUM_ALIEN_COLUMNS 7 #define NUM_ALIEN_ROWS 3 #define X_START_OFFSET 6 #define SPACE_BETWEEN_ALIEN_COLUMNS 5 #define LARGEST_ALIEN_WIDTH 11 #define SPACE_BETWEEN_ROWS 9 #define INVADERS_DROP_BY 4 // pixel amount that invaders move down by #define INVADERS_SPEED 12 // speed of movement, lower=faster. #define INVADER_HEIGHT 8 #define EXPLOSION_GFX_TIME 7 // How long an ExplosionGfx remains on screen before dissapearing #define INVADERS_Y_START MOTHERSHIP_HEIGHT-1 #define AMOUNT_TO_DROP_BY_PER_LEVEL 4 //NEW How much farther down aliens start per new level #define LEVEL_TO_RESET_TO_START_HEIGHT 4 // EVERY MULTIPLE OF THIS LEVEL THE ALIEN y START POSITION WILL RESET TO TOP #define ALIEN_X_MOVE_AMOUNT 1 //number of pixels moved at start of wave #define CHANCEOFBOMBDROPPING 20 // Higher the number the rarer the bomb drop, #define BOMB_HEIGHT 4 #define BOMB_WIDTH 2 #define MAXBOMBS 3 // Max number of bombs allowed to drop at a time // Player settingsc #define TANKGFX_WIDTH 13 #define TANKGFX_HEIGHT 8 #define PLAYER_X_MOVE_AMOUNT 2 #define LIVES 3 //NEW #define PLAYER_EXPLOSION_TIME 10 // How long an ExplosionGfx remains on screen before dissapearing #define PLAYER_Y_START 56 #define PLAYER_X_START 0 #define MISSILE_HEIGHT 4 #define MISSILE_WIDTH 1 #define MISSILE_SPEED 4 // Status of a game object constants #define ACTIVE 0 #define EXPLODING 1 #define DESTROYED 2 // graphics // aliens const unsigned char MotherShipGfx [] PROGMEM = { B00111111,B11111100, B01101101,B10110110, B11111111,B11111111, B00111001,B10011100 }; const unsigned char InvaderTopGfx [] PROGMEM = { B00011000, B00111100, B01111110, B11011011, B11111111, B00100100, B01011010, B10100101 }; const unsigned char InvaderTopGfx2 [] PROGMEM = { B00011000, B00111100, B01111110, B11011011, B11111111, B01011010, B10000001, B01000010 }; const unsigned char PROGMEM InvaderMiddleGfx []= { B00100000,B10000000, B00010001,B00000000, B00111111,B10000000, B01101110,B11000000, B11111111,B11100000, B10111111,B10100000, B10100000,B10100000, B00011011,B00000000 }; const unsigned char PROGMEM InvaderMiddleGfx2 [] = { B00100000,B10000000, B00010001,B00000000, B10111111,B10100000, B10101110,B10100000, B11111111,B11100000, B00111111,B10000000, B00100000,B10000000, B01000000,B01000000 }; const unsigned char PROGMEM InvaderBottomGfx [] = { B00001111,B00000000, B01111111,B11100000, B11111111,B11110000, B11100110,B01110000, B11111111,B11110000, B00111001,B11000000, B01100110,B01100000, B00110000,B11000000 }; const unsigned char PROGMEM InvaderBottomGfx2 [] = { B00001111,B00000000, B01111111,B11100000, B11111111,B11110000, B11100110,B01110000, B11111111,B11110000, B00111001,B11000000, B01000110,B00100000, B10000000,B00010000 }; static const unsigned char PROGMEM ExplosionGfx [] = { B00001000,B10000000, B01000101,B00010000, B00100000,B00100000, B00010000,B01000000, B11000000,B00011000, B00010000,B01000000, B00100101,B00100000, B01001000,B10010000 }; // Player grafix const unsigned char PROGMEM TankGfx [] = { B00000010,B00000000, B00000111,B00000000, B00000111,B00000000, B01111111,B11110000, B11111111,B11111000, B11111111,B11111000, B11111111,B11111000, B11111111,B11111000, }; static const unsigned char PROGMEM MissileGfx [] = { B10000000, B10000000, B10000000, B10000000 }; static const unsigned char PROGMEM AlienBombGfx [] = { B10000000, B01000000, B10000000, B01000000 }; // Game structures struct GameObjectStruct { // base object which most other objects will include signed int X; signed int Y; unsigned char Status; //0 active, 1 exploding, 2 destroyed }; struct AlienStruct { GameObjectStruct Ord; unsigned char ExplosionGfxCounter; // how long we want the ExplosionGfx to last }; struct PlayerStruct { GameObjectStruct Ord; unsigned int Score; unsigned char Lives; //NEW unsigned char Level; unsigned char AliensDestroyed; // count of how many killed so far unsigned char AlienSpeed; // higher the number slower they go, calculated when ever alien destroyed unsigned char ExplosionGfxCounter; // how long we want the ExplosionGfx to last }; // general global variables Adafruit_SSD1306 display(1); //alien global vars //The array of aliens across the screen AlienStruct Alien[NUM_ALIEN_COLUMNS][NUM_ALIEN_ROWS]; AlienStruct MotherShip; GameObjectStruct AlienBomb[MAXBOMBS]; static const int TOTAL_ALIENS=NUM_ALIEN_COLUMNS*NUM_ALIEN_ROWS; //NEW // widths of aliens // as aliens are the same type per row we do not need to store their graphic width per alien in the structure above // that would take a byte per alien rather than just three entries here, 1 per row, saving significnt memory byte AlienWidth[]={8,11,12}; // top, middle ,bottom widths char AlienXMoveAmount=2; signed char InvadersMoveCounter; // counts down, when 0 move invaders, set according to how many aliens on screen bool AnimationFrame=false; // two frames of animation, if true show one if false show the other // Mothership signed char MotherShipSpeed; unsigned int MotherShipBonus; signed int MotherShipBonusXPos; // pos to display bonus at unsigned char MotherShipBonusCounter; // how long bonus amount left on screen // Player global variables PlayerStruct Player; GameObjectStruct Missile; // game variables unsigned int HiScore; bool GameInPlay=false; void setup() { display.begin(SSD1306_SWITCHCAPVCC,OLED_ADDRESS); InitAliens(0); InitPlayer(); pinMode(RIGHT_BUT, INPUT_PULLUP); pinMode(LEFT_BUT, INPUT_PULLUP); pinMode(FIRE_BUT, INPUT_PULLUP); display.setTextSize(1); display.setTextColor(WHITE); EEPROM.get(0,HiScore); if(HiScore==65535) // new unit never written to { HiScore=0; EEPROM.put(0,HiScore); } } void loop() { //NEW if(GameInPlay) { Physics(); UpdateDisplay(); } else AttractScreen(); } void AttractScreen() { display.clearDisplay(); CentreText("Play",0); CentreText("Space Invaders",12); CentreText("Press Fire to start",24); CentreText("Hi Score ",36); display.setCursor(80,36); display.print(HiScore); display.display(); if(digitalRead(FIRE_BUT)==0){ GameInPlay=true; NewGame(); } // CHECK FOR HIGH SCORE RESET, PLAYER MUST HOLD LEFT AND RIGHT TOGETHER if((digitalRead(LEFT_BUT)==0)&(digitalRead(RIGHT_BUT)==0)) { // Reset high score, don't need to worry about debounce as will ony write to EEPROM if changed, so writes a 0 then won't write again // if hiscore still 0 which it will be HiScore=0; EEPROM.put(0,HiScore); } } void Physics() { if(Player.Ord.Status==ACTIVE) { AlienControl(); MotherShipPhysics(); PlayerControl(); MissileControl(); CheckCollisions(); } } unsigned char GetScoreForAlien(int RowNumber) { // returns value for killing and alien at the row indicated switch (RowNumber) { case 0:return 30; case 1:return 20; case 2:return 10; } } void MotherShipPhysics() { if(MotherShip.Ord.Status==ACTIVE) {// spawned, move it MotherShip.Ord.X+=MotherShipSpeed; if(MotherShipSpeed>0) // going left to right , check if off right hand side { if(MotherShip.Ord.X>=SCREEN_WIDTH) { MotherShip.Ord.Status=DESTROYED; } } else // going right to left , check if off left hand side { if(MotherShip.Ord.X+MOTHERSHIP_WIDTH<0) { MotherShip.Ord.Status=DESTROYED; } } } else { // try to spawn mothership if(random(MOTHERSHIP_SPAWN_CHANCE)==1) { // Spawn a mother ship, starts just off screen at top MotherShip.Ord.Status=ACTIVE; // need to set direction if(random(2)==1) // values between 0 and 1 { MotherShip.Ord.X=SCREEN_WIDTH; MotherShipSpeed=-MOTHERSHIP_SPEED; // if we go in here swaps to right to left } else { MotherShip.Ord.X=-MOTHERSHIP_WIDTH; MotherShipSpeed=MOTHERSHIP_SPEED; // set to go left ot right } } } } void PlayerControl() { // user input checks if((digitalRead(RIGHT_BUT)==0)&(Player.Ord.X+TANKGFX_WIDTH<SCREEN_WIDTH)) Player.Ord.X+=PLAYER_X_MOVE_AMOUNT; if((digitalRead(LEFT_BUT)==0)&(Player.Ord.X>0)) Player.Ord.X-=PLAYER_X_MOVE_AMOUNT; if((digitalRead(FIRE_BUT)==0)&(Missile.Status!=ACTIVE)) { Missile.X=Player.Ord.X+(TANKGFX_WIDTH/2); Missile.Y=PLAYER_Y_START; Missile.Status=ACTIVE; } } void MissileControl() { if(Missile.Status==ACTIVE) { Missile.Y-=MISSILE_SPEED; if(Missile.Y+MISSILE_HEIGHT<0) // If off top of screen destroy so can be used again Missile.Status=DESTROYED; } } void AlienControl() { if((InvadersMoveCounter--)<0) { bool Dropped=false; if((RightMostPos()+AlienXMoveAmount>=SCREEN_WIDTH) |(LeftMostPos()+AlienXMoveAmount<0)) // at edge of screen { AlienXMoveAmount=-AlienXMoveAmount; // reverse direction Dropped=true; // and indicate we are dropping } // update the alien postions for(int Across=0;Across<NUM_ALIEN_COLUMNS;Across++) { for(int Down=0;Down<3;Down++) { if(Alien[Across][Down].Ord.Status==ACTIVE) { if(Dropped==false) Alien[Across][Down].Ord.X+=AlienXMoveAmount; else Alien[Across][Down].Ord.Y+=INVADERS_DROP_BY; } } } InvadersMoveCounter=Player.AlienSpeed; AnimationFrame=!AnimationFrame; ///swap to other frame } // should the alien drop a bomb if(random(CHANCEOFBOMBDROPPING)==1) DropBomb(); MoveBombs(); } void MoveBombs(){ for(int i=0;i<MAXBOMBS;i++){ if(AlienBomb[i].Status==ACTIVE) AlienBomb[i].Y+=2; } } void DropBomb() { // if there is a free bomb slot then drop a bomb else nothing happens bool Free=false; unsigned char ActiveCols[NUM_ALIEN_COLUMNS]; unsigned char BombIdx=0; // find a free bomb slot while((Free==false)&(BombIdx<MAXBOMBS)){ if(AlienBomb[BombIdx].Status==DESTROYED) Free=true; else BombIdx++; } if(Free) { unsigned char Columns=0; // now pick and alien at random to drop the bomb // we first pick a column, obviously some columns may not exist, so we count number of remaining cols // first, this adds time but then also picking columns randomly that don't exist may take time also unsigned char ActiveColCount=0; signed char Row; unsigned char ChosenColumn; while(Columns<NUM_ALIEN_COLUMNS){ Row=2; while(Row>=0) { if(Alien[Columns][Row].Ord.Status==ACTIVE) { ActiveCols[ActiveColCount]=Columns; ActiveColCount++; break; } Row--; } Columns++; } // we have ActiveCols array filled with the column numbers of the active cols and we have how many // in ActiveColCount, now choose a column at random ChosenColumn=random(ActiveColCount); // random number between 0 and the amount of columns // we now find the first available alien in this column to drop the bomb from Row=2; while(Row>=0) { if(Alien[ActiveCols[ChosenColumn]][Row].Ord.Status==ACTIVE) { // Set the bomb from this alien AlienBomb[BombIdx].Status=ACTIVE; AlienBomb[BombIdx].X=Alien[ActiveCols[ChosenColumn]][Row].Ord.X+int(AlienWidth[Row]/2); // above sets bomb to drop around invaders centre, here we add a litrle randomness around this pos AlienBomb[BombIdx].X=(AlienBomb[BombIdx].X-2)+random(0,4); AlienBomb[BombIdx].Y=Alien[ActiveCols[ChosenColumn]][Row].Ord.Y+4; break; } Row--; } } } void BombCollisions() { //check bombs collisions for(int i=0;i<MAXBOMBS;i++) { if(AlienBomb[i].Status==ACTIVE) { if(AlienBomb[i].Y>64) // gone off bottom of screen AlienBomb[i].Status=DESTROYED; else { // HAS IT HIT PLAYERS missile if(Collision(AlienBomb[i],BOMB_WIDTH,BOMB_HEIGHT,Missile,MISSILE_WIDTH,MISSILE_HEIGHT)) { // destroy missile and bomb AlienBomb[i].Status=EXPLODING; Missile.Status=DESTROYED; } else { // has it hit players ship if(Collision(AlienBomb[i],BOMB_WIDTH,BOMB_HEIGHT,Player.Ord,TANKGFX_WIDTH,TANKGFX_HEIGHT)) { PlayerHit(); AlienBomb[i].Status=DESTROYED; } } } } } } void PlayerHit() { Player.Ord.Status=EXPLODING; Player.ExplosionGfxCounter=PLAYER_EXPLOSION_TIME; Missile.Status=DESTROYED; } void CheckCollisions() { MissileAndAlienCollisions(); MotherShipCollisions(); BombCollisions(); } void MotherShipCollisions() { if((Missile.Status==ACTIVE)&(MotherShip.Ord.Status==ACTIVE)) { if(Collision(Missile,MISSILE_WIDTH,MISSILE_HEIGHT,MotherShip.Ord,MOTHERSHIP_WIDTH,MOTHERSHIP_HEIGHT)) { MotherShip.Ord.Status=EXPLODING; MotherShip.ExplosionGfxCounter=EXPLOSION_GFX_TIME; Missile.Status=DESTROYED; // generate the score for the mothership hit, note in the real arcade space invaders the score was not random but // just appeared so, a player could infulence its value with clever play, but we'll keep it a little simpler MotherShipBonus=random(4); // a random number between 0 and 3 switch(MotherShipBonus) { case 0:MotherShipBonus=50;break; case 1:MotherShipBonus=100;break; case 2:MotherShipBonus=150;break; case 3:MotherShipBonus=300;break; } Player.Score+=MotherShipBonus; MotherShipBonusXPos=MotherShip.Ord.X; if(MotherShipBonusXPos>100) // to ensure isn't half off right hand side of screen MotherShipBonusXPos=100; if(MotherShipBonusXPos<0) // to ensure isn't half off right hand side of screen MotherShipBonusXPos=0; MotherShipBonusCounter=DISPLAY_MOTHERSHIP_BONUS_TIME; } } } void MissileAndAlienCollisions() { for(int across=0;across<NUM_ALIEN_COLUMNS;across++) { for(int down=0;down<NUM_ALIEN_ROWS;down++) { if(Alien[across][down].Ord.Status==ACTIVE) { if(Missile.Status==ACTIVE) { if(Collision(Missile,MISSILE_WIDTH,MISSILE_HEIGHT,Alien[across][down].Ord,AlienWidth[down],INVADER_HEIGHT)) { // missile hit Alien[across][down].Ord.Status=EXPLODING; Missile.Status=DESTROYED; Player.Score+=GetScoreForAlien(down); Player.AliensDestroyed++; // calc new speed of aliens, note (float) must be before TOTAL_ALIENS to force float calc else // you will get an incorrect result Player.AlienSpeed=((1-(Player.AliensDestroyed/(float)TOTAL_ALIENS))*INVADERS_SPEED); // for very last alien make to fast! if(Player.AliensDestroyed==TOTAL_ALIENS-2) if(AlienXMoveAmount>0) AlienXMoveAmount=ALIEN_X_MOVE_AMOUNT*2; else AlienXMoveAmount=-(ALIEN_X_MOVE_AMOUNT*2); // for very last alien make to super fast! if(Player.AliensDestroyed==TOTAL_ALIENS-1) if(AlienXMoveAmount>0) AlienXMoveAmount=ALIEN_X_MOVE_AMOUNT*4; else AlienXMoveAmount=-(ALIEN_X_MOVE_AMOUNT*4); if(Player.AliensDestroyed==TOTAL_ALIENS) NextLevel(&Player); } } if(Alien[across][down].Ord.Status==ACTIVE) // double check still active afer above code { // check if this alien is in contact with TankGfx if(Collision(Player.Ord,TANKGFX_WIDTH,TANKGFX_HEIGHT,Alien[across][down].Ord,AlienWidth[down],ALIEN_HEIGHT)) PlayerHit(); else { // check if alien is below bottom of screen if(Alien[across][down].Ord.Y+8>SCREEN_HEIGHT) PlayerHit(); } } } } } } bool Collision(GameObjectStruct Obj1,unsigned char Width1,unsigned char Height1,GameObjectStruct Obj2,unsigned char Width2,unsigned char Height2) { return ((Obj1.X+Width1>Obj2.X)&(Obj1.X<Obj2.X+Width2)&(Obj1.Y+Height1>Obj2.Y)&(Obj1.Y<Obj2.Y+Height2)); } int RightMostPos() { //returns x pos of right most alien int Across=NUM_ALIEN_COLUMNS-1; int Down; int Largest=0; int RightPos; while(Across>=0){ Down=0; while(Down<NUM_ALIEN_ROWS){ if(Alien[Across][Down].Ord.Status==ACTIVE) { // different aliens have different widths, add to x pos to get rightpos RightPos= Alien[Across][Down].Ord.X+AlienWidth[Down]; if(RightPos>Largest) Largest=RightPos; } Down++; } if(Largest>0) // we have found largest for this coloum return Largest; Across--; } return 0; // should never get this far } int LeftMostPos() { //returns x pos of left most alien int Across=0; int Down; int Smallest=SCREEN_WIDTH*2; while(Across<NUM_ALIEN_COLUMNS){ Down=0; while(Down<3){ if(Alien[Across][Down].Ord.Status==ACTIVE) if(Alien[Across][Down].Ord.X<Smallest) Smallest=Alien[Across][Down].Ord.X; Down++; } if(Smallest<SCREEN_WIDTH*2) // we have found smalest for this coloum return Smallest; Across++; } return 0; // should nevr get this far } void UpdateDisplay() { int i; display.clearDisplay(); // Mothership bonus display if required if(MotherShipBonusCounter>0) { // mothership bonus display.setCursor(MotherShipBonusXPos,0); display.print(MotherShipBonus); MotherShipBonusCounter--; } else { // draw score and lives, anything else can go above them display.setCursor(0,0); display.print(Player.Score); display.setCursor(SCREEN_WIDTH-7,0); display.print(Player.Lives); } //BOMBS // draw bombs next as aliens have priority of overlapping them for(i=0;i<MAXBOMBS;i++) { if(AlienBomb[i].Status==ACTIVE) display.drawBitmap(AlienBomb[i].X, AlienBomb[i].Y, AlienBombGfx, 2, 4,WHITE); else {// must be destroyed if(AlienBomb[i].Status==EXPLODING) display.drawBitmap(AlienBomb[i].X-4, AlienBomb[i].Y, ExplosionGfx, 4, 8,WHITE); // Ensure on next draw that ExplosionGfx dissapears AlienBomb[i].Status=DESTROYED; } } //Invaders for(int across=0;across<NUM_ALIEN_COLUMNS;across++) { for(int down=0;down<NUM_ALIEN_ROWS;down++) { if(Alien[across][down].Ord.Status==ACTIVE){ switch(down) { case 0: if(AnimationFrame) display.drawBitmap(Alien[across][down].Ord.X, Alien[across][down].Ord.Y, InvaderTopGfx, AlienWidth[down],INVADER_HEIGHT,WHITE); else display.drawBitmap(Alien[across][down].Ord.X, Alien[across][down].Ord.Y, InvaderTopGfx2, AlienWidth[down],INVADER_HEIGHT,WHITE); break; case 1: if(AnimationFrame) display.drawBitmap(Alien[across][down].Ord.X, Alien[across][down].Ord.Y, InvaderMiddleGfx, AlienWidth[down],INVADER_HEIGHT,WHITE); else display.drawBitmap(Alien[across][down].Ord.X, Alien[across][down].Ord.Y, InvaderMiddleGfx2, AlienWidth[down],INVADER_HEIGHT,WHITE); break; default: if(AnimationFrame) display.drawBitmap(Alien[across][down].Ord.X, Alien[across][down].Ord.Y, InvaderBottomGfx, AlienWidth[down],INVADER_HEIGHT,WHITE); else display.drawBitmap(Alien[across][down].Ord.X, Alien[across][down].Ord.Y, InvaderBottomGfx2, AlienWidth[down],INVADER_HEIGHT,WHITE); } } else { if(Alien[across][down].Ord.Status==EXPLODING){ Alien[across][down].ExplosionGfxCounter--; if(Alien[across][down].ExplosionGfxCounter>0) { display.drawBitmap(Alien[across][down].Ord.X, Alien[across][down].Ord.Y, ExplosionGfx, 13, 8,WHITE); } else Alien[across][down].Ord.Status=DESTROYED; } } } } // player if(Player.Ord.Status==ACTIVE) display.drawBitmap(Player.Ord.X, Player.Ord.Y, TankGfx, TANKGFX_WIDTH, TANKGFX_HEIGHT,WHITE); else { if(Player.Ord.Status==EXPLODING) { for(i=0;i<TANKGFX_WIDTH;i+=2) { display.drawBitmap(Player.Ord.X+i, Player.Ord.Y, ExplosionGfx, random(4)+2, 8,WHITE); } Player.ExplosionGfxCounter--; if(Player.ExplosionGfxCounter==0) { Player.Ord.Status=DESTROYED; LoseLife(); } } } //missile if(Missile.Status==ACTIVE) display.drawBitmap(Missile.X, Missile.Y, MissileGfx, MISSILE_WIDTH, MISSILE_HEIGHT,WHITE); // mothership (not bonus if hit) if(MotherShip.Ord.Status==ACTIVE) display.drawBitmap(MotherShip.Ord.X, MotherShip.Ord.Y, MotherShipGfx, MOTHERSHIP_WIDTH, MOTHERSHIP_HEIGHT,WHITE); else { if(MotherShip.Ord.Status==EXPLODING) { for(i=0;i<MOTHERSHIP_WIDTH;i+=2) { display.drawBitmap(MotherShip.Ord.X+i, MotherShip.Ord.Y, ExplosionGfx, random(4)+2, MOTHERSHIP_HEIGHT,WHITE); } MotherShip.ExplosionGfxCounter--; if(MotherShip.ExplosionGfxCounter==0) { MotherShip.Ord.Status=DESTROYED; } } } display.display(); } void LoseLife() { Player.Lives--; if(Player.Lives>0) { DisplayPlayerAndLives(&Player); // clear alien missiles for(int i=0;i<MAXBOMBS;i++) { AlienBomb[i].Status=DESTROYED; AlienBomb[i].Y=0; } // ENABLE PLAYER Player.Ord.Status=ACTIVE; Player.Ord.X=0; } else { GameOver(); } } void GameOver() { GameInPlay=false; display.clearDisplay(); CentreText("Player 1",0); CentreText("Game Over",12); CentreText("Score ",24); display.print(Player.Score); if(Player.Score>HiScore) { CentreText("NEW HIGH SCORE!!!",36); CentreText("**CONGRATULATIONS**",48); } display.display(); if(Player.Score>HiScore){ HiScore=Player.Score; EEPROM.put(0,HiScore); } delay(2500); } void DisplayPlayerAndLives(PlayerStruct *Player) { display.clearDisplay(); CentreText("Player 1",0); CentreText("Score ",12); display.print(Player->Score); CentreText("Lives ",24); display.print(Player->Lives); CentreText("Level ",36); display.print(Player->Level); display.display(); delay(2000); Player->Ord.X=PLAYER_X_START; } void CentreText(const char *Text,unsigned char Y) { // centres text on screen display.setCursor(int((float)(SCREEN_WIDTH)/2-((strlen(Text)*6)/2)),Y); display.print(Text); } void InitPlayer() { Player.Ord.Y=PLAYER_Y_START; Player.Ord.X=PLAYER_X_START; Player.Ord.Status=ACTIVE; Player.Lives=LIVES; Player.Level=0; Missile.Status=DESTROYED; Player.Score=0; } void NextLevel(PlayerStruct *Player) { // reset any dropping bombs int YStart; for(int i=0;i<MAXBOMBS;i++) AlienBomb[i].Status=DESTROYED; AnimationFrame=false; Player->Level++; YStart=((Player->Level-1) % LEVEL_TO_RESET_TO_START_HEIGHT)*AMOUNT_TO_DROP_BY_PER_LEVEL; InitAliens(YStart); AlienXMoveAmount=ALIEN_X_MOVE_AMOUNT; Player->AlienSpeed=INVADERS_SPEED; Player->AliensDestroyed=0; MotherShip.Ord.X=-MOTHERSHIP_WIDTH; MotherShip.Ord.Status=DESTROYED; Missile.Status=DESTROYED; randomSeed(100); DisplayPlayerAndLives(Player); } void NewGame(){ InitPlayer(); NextLevel(&Player); } void InitAliens(int YStart) { for(int across=0;across<NUM_ALIEN_COLUMNS;across++) { for(int down=0;down<3;down++) { // we add down to centralise the aliens, just happens to be the right value we need per row! // we need to adjust a little as row zero should be 2, row 1 should be 1 and bottom row 0 Alien[across][down].Ord.X=X_START_OFFSET+(across*(LARGEST_ALIEN_WIDTH+SPACE_BETWEEN_ALIEN_COLUMNS))-(AlienWidth[down]/2); Alien[across][down].Ord.Y=YStart+(down*SPACE_BETWEEN_ROWS); Alien[across][down].Ord.Status=ACTIVE; Alien[across][down].ExplosionGfxCounter=EXPLOSION_GFX_TIME; } } MotherShip.Ord.Y=0; MotherShip.Ord.X=-MOTHERSHIP_WIDTH; MotherShip.Ord.Status=DESTROYED; } |