document.addEventListener("keydown", (e) => {
    switch (e.key) {
        case "a":
            if (this.state.direction != "right") {
                this.setState({...this.state, nextDirection: "left"});
            }
        break;
        case "s":
            if (this.state.direction != "up") {
                this.setState({...this.state, nextDirection: "down"});
            }
        break;
        case "d":
            if (this.state.direction != "left") {
                this.setState({...this.state, nextDirection: "right"});
            }
        break;
        case "w":
            if (this.state.direction != "down") {
                this.setState({...this.state, nextDirection: "up"});
            }
        break;
    }
});