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CSS

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HTML
!

CSS 

              
                $alive: red;
$dead: white;
$fontFam: 'Titillium Web', arial, helvetica, sans-serif;
$clickHoverColor: #fbb;
* {
  box-sizing: border-box;
  font-family: $fontFam;
}

h1,
#timer,
#controls {
  text-align: center;
}

h1 {
  margin-bottom: 0;
  
  a{
    text-decoration: none;
    color: #333;
  }
  
  span {
    font-size: 14px;
    color: #fff;
    background: #444;
    width: 20px;
    height: 20px;
    display: inline-block;
    line-height: 1.25;
    border-radius: 50%;
    vertical-align: middle;
  }
}

#gol {
  width: 551px;
  margin: auto;
  display: block;
  text-align: center;
  
  p {
    font-size: 14px;
    margin: 0;
    
    &:last-of-type {
      margin-bottom: 20px;
    }
  }
}

.row {
  display: block;
  font-size: 0;
}

.cell {
  background: $dead;
  width: 11px;
  height: 11px;
  margin: 0;
  padding: 0;
  border-right: 1px solid #000;
  border-bottom: 1px solid #000;
  display: inline-block;
}

.row:first-of-type {
  border-top: 1px solid #000;
}

.cell:first-child {
  border-left: 1px solid #000;
  width: 12px;
}

.cell:before {
  content: ' ';
  display: block;
  width: 10px;
  height: 10px;
  border-radius: 50%;
}

.cell.alive:before {
  background: $alive;
}

.cell:hover {
  background: $clickHoverColor;
}

#timer {
  margin-bottom: 10px;
}

#controls {
  margin-top: 10px;
}

#controls button {
  margin-left: 20px;
  background: none;
  border-image: none;
  border: 1px solid #333;
  font-size: 14px;
}

#controls button:first-of-type {
  margin-left: 0;
}

#controls button:hover {
  cursor: pointer;
  background: $clickHoverColor;
}

#controls button:focus {
  outline: none;
}

#controls #glider-gun {
  display: block;
  margin: 15px auto;
}
!

JS 

              
                class GameOfLife extends React.Component {  
  constructor(props) {
    super(props);
    var gameBoard = []
    var setInt;
    for (var i=0; i<this.props.rows; i++) {
      gameBoard.push([]);
      for (var x=0; x<this.props.cols; x++) {
        gameBoard[i].push(Math.round(Math.random()));
      }
    }
    this.state = {
      gameBoard: gameBoard,
      generation: 0,
      isRunning: true
    }
  }
  componentDidMount() {
    //Run game on initial load
    this.setInt = setInterval(this.calcGameBoard.bind(this), 250);
  }
  handleRun() {
    if (!this.state.isRunning) {
      this.setInt = setInterval(this.calcGameBoard.bind(this), 250)
    }
  }
  handlePause() {
    clearInterval(this.setInt)
    this.setState({
      gameBoard: this.state.gameBoard,
      generation: this.state.generation,
      isRunning: false
    })
  }
  handleClear() {
    var cleanBoard = this.state.gameBoard.map((v,i) => {
      return(
        this.state.gameBoard[i].map(() => {
          return 0;
        })
      )
    })
    clearInterval(this.setInt)
    this.setState({
      gameBoard: cleanBoard,
      generation: 0,
      isRunning: false
    })
  }
  handleViewGlider(gliderBoard) {
    clearInterval(this.setInt)
    this.setState({
      gameBoard: gliderBoard,
      generation: 0,
      isRunning: false
    })
    this.setInt = setInterval(this.calcGameBoard.bind(this), 250)
  }
  calcGameBoard() {
    //Copy current gameboard to new array
    var nextBoard = []
    for (var cr=0; cr<this.state.gameBoard.length; cr++) {
      nextBoard.push([])
      for (var cc=0; cc<this.state.gameBoard[cr].length; cc++) {
        nextBoard[cr].push(this.state.gameBoard[cr][cc])
      }
    }
    
    //Calculate next board
    var globalSum = 0
    for (var r=0; r<this.state.gameBoard.length; r++) {
      for (var c=0; c<this.state.gameBoard[r].length; c++) {
        var sum = 0
        if ( r === 0 && c === 0 ) {
          //Top Left Corner
          sum = this.state.gameBoard[this.state.gameBoard.length-1][this.state.gameBoard[r].length-1] +
                this.state.gameBoard[this.state.gameBoard.length-1][c] +
                this.state.gameBoard[this.state.gameBoard.length-1][c+1] +
                this.state.gameBoard[r][this.state.gameBoard[r].length-1] +
                this.state.gameBoard[r][c+1] +
                this.state.gameBoard[r+1][this.state.gameBoard[r].length-1] +
                this.state.gameBoard[r+1][c] +
                this.state.gameBoard[r+1][c+1]
          globalSum += sum
          if (this.state.gameBoard[r][c] === 1) {
            if (sum < 2) { 
              nextBoard[r][c] = 0 
            } else if (sum === 2 || sum === 3) {
              nextBoard[r][c] = 1
            } else if (sum > 3) {
              nextBoard[r][c] = 0
            }
          } else if (this.state.gameBoard[r][c] === 0 && sum === 3) {
              nextBoard[r][c] = 1
          }
        } else if (r === 0 && c === this.state.gameBoard[r].length - 1) {
          //Top Right Corner
          sum = this.state.gameBoard[this.state.gameBoard.length-1][c-1] +
                this.state.gameBoard[this.state.gameBoard.length-1][c] +
                this.state.gameBoard[this.state.gameBoard.length-1][0] +
                this.state.gameBoard[r][c-1] +
                this.state.gameBoard[r][0] +
                this.state.gameBoard[r+1][c-1] +
                this.state.gameBoard[r+1][c] +
                this.state.gameBoard[r+1][0]
          globalSum += sum
          if (this.state.gameBoard[r][c] === 1) {
            if (sum < 2) { 
              nextBoard[r][c] = 0 
            } else if (sum === 2 || sum === 3) {
              nextBoard[r][c] = 1
            } else if (sum > 3) {
              nextBoard[r][c] = 0
            }
          } else if (this.state.gameBoard[r][c] === 0 && sum === 3) {
              nextBoard[r][c] = 1
          } 
        } else if (r === this.state.gameBoard.length - 1 && c === 0 ) {
          //Bottom Left Corner
          sum = this.state.gameBoard[r-1][this.state.gameBoard[r].length-1] +
                this.state.gameBoard[r-1][c] +
                this.state.gameBoard[r-1][c+1] +
                this.state.gameBoard[r][this.state.gameBoard[r].length-1] +
                this.state.gameBoard[r][c+1] +
                this.state.gameBoard[0][this.state.gameBoard[r].length-1] +
                this.state.gameBoard[0][c] +
                this.state.gameBoard[0][c+1]
          globalSum += sum
          if (this.state.gameBoard[r][c] === 1) {
            if (sum < 2) { 
              nextBoard[r][c] = 0 
            } else if (sum === 2 || sum === 3) {
              nextBoard[r][c] = 1
            } else if (sum > 3) {
              nextBoard[r][c] = 0
            }
          } else if (this.state.gameBoard[r][c] === 0 && sum === 3) {
              nextBoard[r][c] = 1
          }
        } else if (r === this.state.gameBoard.length - 1 && c === this.state.gameBoard[r].length - 1) {
          //Bottom Right Corner
          sum = this.state.gameBoard[r-1][c-1] +
                this.state.gameBoard[r-1][c] +
                this.state.gameBoard[r-1][0] +
                this.state.gameBoard[r][c-1] +
                this.state.gameBoard[r][0] +
                this.state.gameBoard[0][c-1] +
                this.state.gameBoard[0][c] +
                this.state.gameBoard[0][0]
          globalSum += sum
          if (this.state.gameBoard[r][c] === 1) {
            if (sum < 2) { 
              nextBoard[r][c] = 0 
            } else if (sum === 2 || sum === 3) {
              nextBoard[r][c] = 1
            } else if (sum > 3) {
              nextBoard[r][c] = 0
            }
          } else if (this.state.gameBoard[r][c] === 0 && sum === 3) {
              nextBoard[r][c] = 1
          }
        } else if (r === 0 ) {
          //Top Edge
          sum = this.state.gameBoard[this.state.gameBoard.length-1][c-1] +
                this.state.gameBoard[this.state.gameBoard.length-1][c] +
                this.state.gameBoard[this.state.gameBoard.length-1][c+1] +
                this.state.gameBoard[r][c-1] +
                this.state.gameBoard[r][c+1] +
                this.state.gameBoard[r+1][c-1] +
                this.state.gameBoard[r+1][c] +
                this.state.gameBoard[r+1][c+1]
          globalSum += sum
          if (this.state.gameBoard[r][c] === 1) {
            if (sum < 2) { 
              nextBoard[r][c] = 0 
            } else if (sum === 2 || sum === 3) {
              nextBoard[r][c] = 1
            } else if (sum > 3) {
              nextBoard[r][c] = 0
            }
          } else if (this.state.gameBoard[r][c] === 0 && sum === 3) {
              nextBoard[r][c] = 1
          } 
        } else if (c === 0) {
          //Left Edge
          sum = this.state.gameBoard[r-1][this.state.gameBoard[r].length-1] +
                this.state.gameBoard[r-1][c] +
                this.state.gameBoard[r-1][c+1] +
                this.state.gameBoard[r][this.state.gameBoard[r].length-1] +
                this.state.gameBoard[r][c+1] +
                this.state.gameBoard[r+1][this.state.gameBoard[r].length-1] +
                this.state.gameBoard[r+1][c] +
                this.state.gameBoard[r+1][c+1]
          globalSum += sum
          if (this.state.gameBoard[r][c] === 1) {
            if (sum < 2) { 
              nextBoard[r][c] = 0 
            } else if (sum === 2 || sum === 3) {
              nextBoard[r][c] = 1
            } else if (sum > 3) {
              nextBoard[r][c] = 0
            }
          } else if (this.state.gameBoard[r][c] === 0 && sum === 3) {
              nextBoard[r][c] = 1
          }
        } else if (c === this.state.gameBoard[r].length - 1) {
          //Right Edge
          sum = this.state.gameBoard[r-1][c-1] +
                this.state.gameBoard[r-1][c] +
                this.state.gameBoard[r-1][0] +
                this.state.gameBoard[r][c-1] +    
                this.state.gameBoard[r][0] +
                this.state.gameBoard[r+1][c-1] +
                this.state.gameBoard[r+1][c] +
                this.state.gameBoard[r+1][0]
          globalSum += sum
          if (this.state.gameBoard[r][c] === 1) {
            if (sum < 2) { 
              nextBoard[r][c] = 0 
            } else if (sum === 2 || sum === 3) {
              nextBoard[r][c] = 1
            } else if (sum > 3) {
              nextBoard[r][c] = 0
            }
          } else if (this.state.gameBoard[r][c] === 0 && sum === 3) {
              nextBoard[r][c] = 1
          }
        } else if (r === this.state.gameBoard.length - 1) {
          //Bottom Edge
          sum = this.state.gameBoard[r-1][c-1] +
                this.state.gameBoard[r-1][c] +
                this.state.gameBoard[r-1][c+1] +
                this.state.gameBoard[r][c-1] +    
                this.state.gameBoard[r][c+1] +
                this.state.gameBoard[0][c-1] +
                this.state.gameBoard[0][c] +
                this.state.gameBoard[0][c+1]
          globalSum += sum
          if (this.state.gameBoard[r][c] === 1) {
            if (sum < 2) { 
              nextBoard[r][c] = 0 
            } else if (sum === 2 || sum === 3) {
              nextBoard[r][c] = 1
            } else if (sum > 3) {
              nextBoard[r][c] = 0
            }
          } else if (this.state.gameBoard[r][c] === 0 && sum === 3) {
              nextBoard[r][c] = 1
          }  
        } else {
          //The MIDDLE
          sum = this.state.gameBoard[r-1][c-1] +
                this.state.gameBoard[r-1][c] +
                this.state.gameBoard[r-1][c+1] +
                this.state.gameBoard[r][c-1] +    
                this.state.gameBoard[r][c+1] +
                this.state.gameBoard[r+1][c-1] +
                this.state.gameBoard[r+1][c] +
                this.state.gameBoard[r+1][c+1]
          globalSum += sum
          if (this.state.gameBoard[r][c] === 1) {
            if (sum < 2) { 
              nextBoard[r][c] = 0 
            } else if (sum === 2 || sum === 3) {
              nextBoard[r][c] = 1
            } else if (sum > 3) {
              nextBoard[r][c] = 0
            }
          } else if (this.state.gameBoard[r][c] === 0 && sum === 3) {
              nextBoard[r][c] = 1
          }  
        }
      } //end inner loop
    } //end outer loop
    if ( globalSum > 0 ) {
      this.state.generation++
      this.setState({
        gameBoard: nextBoard,
        generation: this.state.generation,
        isRunning: true
      })
    } else {
      this.handlePause()
    }
  }
  drawGameBoard() {
    return(
      this.state.gameBoard.map((v,i) => {
        return(
          <div className="row" data-row={i}>
            { this.state.gameBoard[i].map((v,i) => {
                switch(v) {
                  case 0:
                    return <div className="cell" onClick={this.toggleCellLife.bind(this)} data-cell={i}></div>
                  case 1:
                    return <div className="cell alive" onClick={this.toggleCellLife.bind(this)} data-cell={i}></div>
                  default:
                    break;
                }
              }, this)
            }
          </div>
        )
      }, this)
    )
  }
  toggleCellLife(e) {
    var col = e.target.dataset.cell
    var row = e.target.parentElement.dataset.row
    var newBoard = this.state.gameBoard
    switch(newBoard[row][col]) {
      case 0:
        newBoard[row][col] = 1;
        break;
      case 1:
        newBoard[row][col] = 0;
        break;
    }
    this.setState({
      gameBoard: newBoard,
      generation: this.state.generation,
      isPaused: this.state.isPaused
    })
  }
  render() {
    return ( 
      <div id="gol">
        <h1>
          <a href="https://en.wikipedia.org/wiki/Conway%27s_Game_of_Life" target="_blank">Conway's Game of Life <span>?</span></a>
        </h1>
        <p>Add cells to game board at any time.</p>
        <p>Pause game to add multiple cells to board.</p>
        <Timer generation={this.state.generation} />
        <div id="game-board">
          {this.drawGameBoard(this.state)}
        </div>
        <Controls board={this.state.gameBoard} run={this.handleRun.bind(this)} pause={this.handlePause.bind(this)} clear={this.handleClear.bind(this)} viewGlider={this.handleViewGlider.bind(this)} />
      </div>
      )
  }
}

class Timer extends React.Component {
  render() {
    return(
      <div id="timer">
        Generation: {this.props.generation}
      </div>
    )
  }
}

class Controls extends React.Component {
  run() {
    this.props.run()
  }
  pause() {
    this.props.pause()
  }
  clear() {
    this.props.clear()
  }
  viewGlider() {
    //Create a clean board
    var gliderBoard = this.props.board.map((v,i) => {
      return(
        this.props.board[i].map(() => {
          return 0;
        })
      )
    })
    //Set board values for glider gun layout
    gliderBoard[1][25] = 1;
    gliderBoard[2][23] = 1;
    gliderBoard[2][25] = 1;
    gliderBoard[3][13] = 1;
    gliderBoard[3][14] = 1;
    gliderBoard[3][21] = 1;
    gliderBoard[3][22] = 1;
    gliderBoard[3][35] = 1;
    gliderBoard[3][36] = 1;
    gliderBoard[4][12] = 1;
    gliderBoard[4][16] = 1;
    gliderBoard[4][21] = 1;
    gliderBoard[4][22] = 1;
    gliderBoard[4][35] = 1;
    gliderBoard[4][36] = 1;
    gliderBoard[5][1] = 1;
    gliderBoard[5][2] = 1;
    gliderBoard[5][11] = 1;
    gliderBoard[5][17] = 1;
    gliderBoard[5][21] = 1;
    gliderBoard[5][22] = 1;
    gliderBoard[6][1] = 1;
    gliderBoard[6][2] = 1;
    gliderBoard[6][11] = 1;
    gliderBoard[6][15] = 1;
    gliderBoard[6][17] = 1;
    gliderBoard[6][18] = 1;
    gliderBoard[6][23] = 1;
    gliderBoard[6][25] = 1;
    gliderBoard[7][11] = 1;
    gliderBoard[7][17] = 1;
    gliderBoard[7][25] = 1;
    gliderBoard[8][12] = 1;
    gliderBoard[8][16] = 1;
    gliderBoard[9][13] = 1;
    gliderBoard[9][14] = 1;
    //Send glider gun array up to game board
    this.props.viewGlider(gliderBoard)
  }
  render() {
    return(
      <div id="controls">
        <button id="run" onClick={this.run.bind(this)}>Run</button>
        <button id="pause" onClick={this.pause.bind(this)}>Pause</button>
        <button id="clear" onClick={this.clear.bind(this)}>Clear</button>
        <button id="glider-gun" onClick={this.viewGlider.bind(this)}>View Glider Gun</button>
      </div>
    )
  }
}

ReactDOM.render(<GameOfLife rows={30} cols={50} />, document.body);
!
999px

Console