Simple Snake Game

Rabi Roshan — Wed, 20 May 2020 10:58:32 +0000

Develop a simple snake game using vanilla javascript, html and css. Show Demo

NOTE: READ COMMENTS TO UNDERSTAND THE CODE ✌🏻

NOTE: YOU CAN SKIP TO STEP 4 TO READ THE ACTUAL CODE IN JS

LET US START:

Create the the base files:
- index.html
- main.css
- jscript.js

Add the following content to index.html:


<!DOCTYPE  html>
<html>
<head  lang="en">
    <meta  charset="UTF-8"  />
    <meta  name="viewport"  content="width=device width,initial-scale=1"  />

    <title>Snake v8</title>

    <!-- Link our styles from main.css -->
    <link  rel="stylesheet"  type="text/css" href="main.css"  />
</head>

<body>
    <!-- #gameContainer is the main game board-->
    <div  class="gameContainer"  id="gameContainer"></div>

    <!-- #scoreContainer contains the scores -->
    <div  id="scoreContainer">
        <div  class="scoreBoard">Food: <span id="pointsEarned">0</span></div>
        <div  class="scoreBoard">Blocks: <span  id="blocksTravelled">0</span></div>
    </div>

    <!-- #onScreenControllers contains the navigation buttons for mobile screens -->
    <div  id="mobileControllers">
        <button  id="leftButton">◀️</button>
        <div>
            <button  id="upButton">🔼</button>
            <button  id="downButton">🔽</button>
        </div>
        <button  id="rightButton">▶️</button>
    </div>
</body>

<!-- #Load our jscript.js containing the game logic -->
<script  src="jscript.js"></script>

</html>

Add the following content to main.css:

body {
    background-color: darkslategrey;
    text-align: center;
}

/* GAME BOARD STYLES */
#gameContainer {
    /*
    width and height of .gameBoardPixel should 1/40 of the width and height of #gameContainer,
    because it is used in calculation in the jscript.js file
    */
    width: 40vw;
    height: 40vw;
    margin: 2vw  auto;
    background-color: #0c1021;
    border: solid  10px  slategrey;
    border-radius: 10px;

    -webkit-box-shadow: 0px  0px  20px  3px  rgba(0, 0, 0, 0.6);
    -moz-box-shadow: 0px  0px  20px  3px  rgba(0, 0, 0, 0.6);
    box-shadow: 0px  0px  20px  3px  rgba(0, 0, 0, 0.6);
}

.gameBoardPixel {
    /*
    width and height of .gameBoardPixel should 1/40 of the width and height of #gameContainer,
    because it is used in calculation in the jscript.js file
    */
    width: 1vw;
    height: 1vw;
    border-radius: 10px;
    float: left;
}
/* GAME BOARD STYLES END*/

/* SNAKE STYLES */
.snakeBodyPixel {
    background-color: #fd6401;
    box-shadow: 0  0  5px  #fd6401;
}
/* SNAKE STYLES END*/

/* FOOD STYLES */
.food {
    background-color: #68e768;
}
/* FOOD STYLES END*/

/* SCORE STYLES */
#scoreContainer {
    width: 40vw;
    display: flex;
    margin: auto;
    justify-content: space-around;
}

.scoreBoard {
    border-radius: 10px;
    border: solid  5px  slategrey;
    color: dimgray;
    background-color: #0c1021;
    display: inline-block;
    padding: 1vw;
    width: 40%;

    -webkit-box-shadow: 0px  0px  20px  3px  rgba(0, 0, 0, 0.6);
    -moz-box-shadow: 0px  0px  20px  3px  rgba(0, 0, 0, 0.6);
    box-shadow: 0px  0px  20px  3px  rgba(0, 0, 0, 0.6);
}
/* SCORE STYLES END */

/* Hide #onScreenControllers on desktop */
#onScreenControllers {
    display: none;
}

@media  only  screen  and (max-width: 768px) {
    /* MOBILE STYLES*/

    #gameContainer {
        width: 80vw;
        height: 80vw;
    }

    .gameBoardPixel {
        width: 2vw;
        height: 2vw;
    }

    #scoreContainer {
        width: 80vw;
    }

    #onScreenControllers {
        width: 80vw;
        margin: 5vw  auto;
        display: flex;
        justify-content: space-evenly;
        align-items: center;
    }

    #onScreenControllers  >  div {
        display: flex;
        flex-direction: column;
    }

    #onScreenControllers  button {
        background-color: transparent;
        height: 20vw;
        width: 20vw;
        font-size: 10vw;
        border: none;
    }

    #onScreenControllers  button:focus {
        outline: none;
    }

    #onScreenControllers  button:active {
        background-color: slategray;
    }
}

Finally, we will write the JavaScript code in jscript.js where the actual logic is written.

Initialize the scores:


let  totalFoodAte  =  0;
let  totalDistanceTravelled  =  0;

Code for the Game Board pixels:


const  gameContainer  =  document.getElementById("gameContainer");
const  createGameBoardPixels  = () => {
    // Populate the [#gameContainer] div with small div's representing game pixels
    for (let  i  =  1; i  <=  1600; ++i) {
        gameContainer.innerHTML  =  `${gameContainer.innerHTML} <div class="gameBoardPixel" id="pixel${i}"></div>`;
    }
};
// This variable always holds the updated array of game pixels created by createGameBoardPixels() :
const  gameBoardPixels  =  document.getElementsByClassName("gameBoardPixel");

Code for the Food:


let  currentFoodPostion  =  0; // Initially set to 0
const  createFood  = () => {
    // Remove previous food;
    gameBoardPixels[currentFoodPostion].classList.remove("food");

    // Create new food
    currentFoodPostion  =  Math.random();
    currentFoodPostion  =  Math.floor(currentFoodPostion  *  1600);
    gameBoardPixels[currentFoodPostion].classList.add("food");
};

Code for the Snake 🐍:

Code related to the Direction of the snake:


// Direction codes (Keyboard key codes for arrow keys):
const  LEFT_DIR  =  37;
const  UP_DIR  =  38;
const  RIGHT_DIR  =  39;
const  DOWN_DIR  =  40;

// Set snake direction initially to right
let  snakeCurrentDirection  =  RIGHT_DIR;

const  changeDirection  =  newDirectionCode  => {
    // Change the direction of the snake
    if (newDirectionCode  ==  snakeCurrentDirection) return;
    if (newDirectionCode  ==  LEFT_DIR  &&  snakeCurrentDirection  != RIGHT_DIR) {
        snakeCurrentDirection  =  newDirectionCode;
    } else  if (newDirectionCode  ==  UP_DIR  &&  snakeCurrentDirection  !=  DOWN_DIR) {
        snakeCurrentDirection  =  newDirectionCode;
    } else  if (newDirectionCode  ==  RIGHT_DIR  && snakeCurrentDirection  !=  LEFT_DIR) {
        snakeCurrentDirection  =  newDirectionCode;
    } else  if (newDirectionCode  ==  DOWN_DIR  &&  snakeCurrentDirection  !=  UP_DIR) {
        snakeCurrentDirection  =  newDirectionCode;
    }
};

Code related to the Movement of the snake:


// Let the starting position of the snake be at the middle of game board
let  currentSnakeHeadPosition  =  799;
let  snakeLength  =  1000; // Initial length of the snake = 1000

// Move snake continously by calling this function repeatedly :
const  moveSnake  = () => {
    switch (snakeCurrentDirection) {
        case  LEFT_DIR:
            --currentSnakeHeadPosition;
            const  isSnakeHeadAtLastGameBoardPixelTowardsLeft  = currentSnakeHeadPosition  %  40  ==  39  ||  currentSnakeHeadPosition  <  0;
            if (isSnakeHeadAtLastGameBoardPixelTowardsLeft) {
                currentSnakeHeadPosition  =  currentSnakeHeadPosition  +  40;
            }
            break;

        case  UP_DIR:
            currentSnakeHeadPosition  =  currentSnakeHeadPosition  -  40;
            const  isSnakeHeadAtLastGameBoardPixelTowardsUp  = currentSnakeHeadPosition  <  0;
            if (isSnakeHeadAtLastGameBoardPixelTowardsUp) {
                currentSnakeHeadPosition  =  currentSnakeHeadPosition  +  1600;
            }
            break;

        case  RIGHT_DIR:
            ++currentSnakeHeadPosition;
            const  isSnakeHeadAtLastGameBoardPixelTowardsRight  = currentSnakeHeadPosition  %  40  ==  0;
            if (isSnakeHeadAtLastGameBoardPixelTowardsRight) {
                currentSnakeHeadPosition  =  currentSnakeHeadPosition  -  40;
            }
            break;

        case  DOWN_DIR:
            currentSnakeHeadPosition  =  currentSnakeHeadPosition  +  40;
            const  isSnakeHeadAtLastGameBoardPixelTowardsDown  = currentSnakeHeadPosition  >  1599;
            if (isSnakeHeadAtLastGameBoardPixelTowardsDown) {
                currentSnakeHeadPosition  =  currentSnakeHeadPosition  -  1600;
            }
            break;

        default:
            break;
    }
    let  nextSnakeHeadPixel  = gameBoardPixels[currentSnakeHeadPosition];

    // Kill snake if it bites itself:
    if (nextSnakeHeadPixel.classList.contains("snakeBodyPixel")) {
        // Stop moving the snake
        clearInterval(moveSnakeInterval);
        if (!alert(`You have ate ${totalFoodAte} food by travelling ${totalDistanceTravelled} blocks.`))
        window.location.reload();
    }

    // If not killed add the snake body:
    nextSnakeHeadPixel.classList.add("snakeBodyPixel");

    // This fuction removes the snake body from the end of the snake as it moves.
    // Also note that snakeLength is used as the timeout interval
    setTimeout(() => {
        nextSnakeHeadPixel.classList.remove("snakeBodyPixel");
    }, snakeLength);

    // Update total distance travelled
    totalDistanceTravelled++;
    // Update in UI:
    document.getElementById("blocksTravelled").innerHTML  = totalDistanceTravelled;

    // If snike bites the food:
    if (currentSnakeHeadPosition  ==  currentFoodPostion) {
        // Update total food ate
        totalFoodAte++;
        // Update in UI:
        document.getElementById("pointsEarned").innerHTML  =  totalFoodAte;
        // Increase Snake length:
        snakeLength  =  snakeLength  +  100;
        // Create new food:
        createFood();
    }
};

Code to start the game using the above logic:


// Create game board pixels:
createGameBoardPixels();

// Create initial food:
createFood();

// Move snake:
// The variable, "moveSnakeInterval" is used to stop the snake on snake killed.
var  moveSnakeInterval  =  setInterval(moveSnake, 80);

// Call change direction function on keyboard key-down event:
addEventListener("keydown", e  =>  changeDirection(e.keyCode));

// CONFIGURE THE ON SCREEN CONTROLLERS:
const  leftButton  =  document.getElementById("leftButton");
const  rightButton  =  document.getElementById("rightButton");
const  upButton  =  document.getElementById("upButton");
const  downButton  =  document.getElementById("downButton");

leftButton.onclick  = () =>  changeDirection(LEFT_DIR);
rightButton.onclick  = () =>  changeDirection(RIGHT_DIR);
upButton.onclick  = () =>  changeDirection(UP_DIR);
downButton.onclick  = () =>  changeDirection(DOWN_DIR);

DEV Community: Rabi Roshan

Simple Snake Game

Develop a simple snake game using vanilla javascript, html and css. Show Demo

NOTE: READ COMMENTS TO UNDERSTAND THE CODE ✌🏻

NOTE: YOU CAN SKIP TO STEP 4 TO READ THE ACTUAL CODE IN JS

LET US START:

Completed project available at Github. Feel free to create PR's 😊.