- [x] `createBoard()` - [x] `initialiseBoard()` - [x] `addMine()` - [x] `revealZeroNeighbours()` - [ ] `revealTile()` - [x] `markTile()` - [ ] `endGame()` - [ ] test all functions
createBoard()initialiseBoard()addMine()revealZeroNeighbours()revealTile()markTile()endGame()