Fly away

Screenshot

Screenshot

A game is not much fun without something happening on the screen. To begin with, we will show a circle that we can steer with the arrow keys on the keyboard.

Implementation

The first two lines of the main function uses the functions screen_width() and screen_height() to get the width and height of the application window. These values are divided by 2 to get the coordinates of the center of the window, and stored in the variables x and y. These variables will be used to decide where to draw the circle on the screen.

    let mut x = screen_width() / 2.0;
    let mut y = screen_height() / 2.0;

Handle keyboard input

Inside the main loop we will still clear the background as it should be done in each frame. After that there are four if statements that check if any of the arrow keys on the keyboard has been pressed. The variables x and y are changed to move the circle in the corresponding direction.

The function is_key_down() returns true if the given key is being pressed during the current frame. The argument is of the enum KeyCode that contains all keys available on the keyboard.

Info

You can read more about how the Rust enum feature works in the Rust book.

        if is_key_down(KeyCode::Right) {
            x += 1.0;
        }
        if is_key_down(KeyCode::Left) {
            x -= 1.0;
        }
        if is_key_down(KeyCode::Down) {
            y += 1.0;
        }
        if is_key_down(KeyCode::Up) {
            y -= 1.0;
        }

Info

You can find other available keys in the documentation of KeyCode.

Draw a circle

Finally we will draw a circle on the screen at the coordinates in x and y. The circle has a radius of 16 and will be drawn in a yellow color.

        draw_circle(x, y, 16.0, YELLOW);

Info

Macroquad has several constants for common colors, and you can also use the macro color_u8 to create a color with specific values for red, green, blue, and transparency.

The other shapes that can be drawn with Macroquad are described in the documentation of Macroquad’s Shape API.

Challenge

Change the value added to x and y to define how fast the circle will move.

Source

The source of main.rs should look like this:

use macroquad::prelude::*;

#[macroquad::main("My game")]
async fn main() {
    let mut x = screen_width() / 2.0;
    let mut y = screen_height() / 2.0;

    loop {
        clear_background(DARKPURPLE);

        if is_key_down(KeyCode::Right) {
            x += 1.0;
        }
        if is_key_down(KeyCode::Left) {
            x -= 1.0;
        }
        if is_key_down(KeyCode::Down) {
            y += 1.0;
        }
        if is_key_down(KeyCode::Up) {
            y -= 1.0;
        }

        draw_circle(x, y, 16.0, YELLOW);

        next_frame().await
    }
}

When you run the game, a yellow circle will appear in the middle of the window. Try using the arrow keys to move the circle around.

Quiz

Try your newfound knowledge by answering this quiz before continuing.

Agical