Refactor by using new Game class.
Set grid's size dynamically via num_cols/rows passed into Game constructor.
Game#genFood() sets Food on randGridSqr.
Game#move if nextCoorSqr has an obj, end game.
Game init code calls this.genFood().
Game#move() allows eating AND ends game if snake runs into itself.
Increase grid size and remove .col border.
Code Game.intervalTime prop that inits to (1000/2) (2x/second).
Change setInterval() time from hard-code to game.intervalTime.