Uncaught TypeError: Cannot read property 'drawHTMLToken' of undefined

const game = new Game();

document.getElementById("begin-game").addEventListener("click", function() {
    game.startGame();
    this.style.display = 'none';
    document.getElementById('play-area').style.opacity = '1';
});

class Board {
    constructor() {
        this.rows = 6;
        this.columns = 7;
        this.spaces = this.createSpaces();
    }
    createSpaces() {
       const spaces = [];

       for (let x = 0; x < this.columns; x++) {
          const col = [];

           for (let y = 0; y < this.rows; y++) {
               const space = new Space(x, y);
               col.push(space);
           }
           spaces.push(col);
       }
       return spaces;
    }

    drawHTMLBoard() {
        for (let col of this.spaces) {
            for (let space of col) {
                space.drawSVGSpace();
            }
        }
    }
}



class Game {
    constructor() {
        this.board =  new Board();
        this.players = this.createPlayers();
        this.ready = false;
    }

    get activePlayer() {
        return this.players.find(player => player.active);
    }

    createPlayers() {
       const players = [new Player("Player 1", 1, "#e15258", true),
                        new Player("Player 2", 2, "#e59a13")];
       return players;
    }  

    startGame() {
       this.board.drawHTMLBoard();
       this.activePlayer.activeToken.drawHTMLToken();
       this.ready = true;
    }

}


class Player {
    constructor(name, id, color, active = false) {
      this.name = name;
      this.id = id;
      this.color = color;
      this.active = active;
      this.tokens = this.createTokens(21);
    }
    createTokens(num) {
      const tokens = [];

      for (let i = 0; i<num.length; i++) {
          let token = new Token(i, this);
          tokens.push(token);
      }

      return tokens;
    }

    get unusedTokens() {
        return this.tokens.filter(token => !token.dropped);
    }

    get activeToken() {
       return this.unusedTokens[0];
    }
}


class Space {
    constructor(x, y) {
        this.x = x;
        this.y = y;
        this.id = `space-${x}-${y}`;
        this.token = null;
        this.diameter = 76;
        this.radius = this.diameter/2;
    }

    drawSVGSpace() {
        const svgSpace = document.createElementNS("http://www.w3.org/2000/svg", "circle");

        svgSpace.setAttributeNS(null, "id", this.id);
        svgSpace.setAttributeNS(null, "cx", (this.x * this.diameter) + this.radius);
        svgSpace.setAttributeNS(null, "cy", (this.y * this.diameter) + this.radius);
        svgSpace.setAttributeNS(null, "r", this.radius - 8);
        svgSpace.setAttributeNS(null, "fill", "black");
        svgSpace.setAttributeNS(null, "stroke", "none");

        document.getElementById("mask").appendChild(svgSpace);   

    }

}


class Token {
  constructor(index, owner) {  
    this.owner = owner;
    this.id = `token-${index}-${owner.id}`;
    this.dropped = false;
  }
  drawHTMLToken() {
      const token = document.createElement("div");
      token.setAttribute("id", this.id);
      token.setAttribute("class", "token");
      token.style.backgroundColor = this.owner.color;
      document.getElementById("game-board-underlay").appendChild(token);
  }

  get htmlToken() {
    return this.drawHTMLToken();
  }
}