fc64js
fc64js - Tutorial - Snake (js)
Eating the fruit
Detecting the fact that the snake’s head (i.e. snake.body[0]) occupies the same world coordinates as the fruit is very simple - both are instances of Vec2 which offers a convenient equals function that returns true if both objects have equal x values and equal y values
Reacting to this collision scenario is also quite straightforward - we’ll need to grow the snake.body by one segment (i.e. append a segment that occupies the same position as the current tip of the tail), and we’ll need to move the fruit to another random position in the game world (to simulate the removal of the old one and creation of a new one)
Note that once the next snake.update is processed the newly added tip of the tail will be one space “behind” the penultimate segment as within update the new tail tip copies the next segments (identical) coordinates (i.e. no change to its location) while all other segments shuffle up by one position. Don’t worry about the fact that the snake will have two body segments occupying the same space for one tick (a mere 60th of a second) - it doesn’t affect gameplay
Here’s the code we’ll need to add:
function romLoop() {
...
snake.update();
if (snake.body[0].equals(fruit)) {
const tailTip = snake.body[snake.body.length - 1];
snake.body.push(new Vec2(tailTip.x, tailTip.y));
fruit.x = randomInt(0, 15);
fruit.y = randomInt(0, 15);
}
...
Now if we refresh the browser we’ll see that the snake can eat the fruit, and when it does so it grows by one segment and a “new” piece of fruit is randomly placed in the world:
Jump to step: Introduction · Project setup · Creating the snake · Drawing the snake · Moving the snake · Throttling the speed · Input handling · Placing the fruit · Eating the fruit · Losing the game · Managing state · Playing sound effects · Bug fixing · Distribution