Text-based 2048 clone

2048.py

#!/usr/bin/env python3
from random import randint

size = 4
score = 0
grid = [[0 for i in range(size)] for i in range(size)]

def display(grid):
    print()
    for i in range(size):
        for j in range(size):
            print(str(grid[i][j]).center(4), end=' ')
        print('\n')

def isFull(grid):
    for i in range(size):
        for j in range(size):
            if grid[i][j] == 0:
                return False
    return True

def spawnNumber(grid):
    if isFull(grid):
        return
    i, j = -1, -1
    while i < 0 or grid[i][j] != 0:
        i = randint(0, size-1)
        j = randint(0, size-1)
    grid[i][j] = 2 if randint(1, 10) > 1 else 4

def rotate(grid, direction):
    if direction == -1:
        return
    new = [[0 for i in range(size)] for i in range(size)]
    for i in range(size):
        for j in range(size):
            if direction == +1:
                new[i][j] = grid[size-i-1][size-j-1]
            elif direction == -1j:
                new[i][j] = grid[size-j-1][i]
            elif direction == +1j:
                new[i][j] = grid[j][size-i-1]
    grid[:] = new

def move(grid, direction):
    global score
    if direction == 0:
        return
    original = grid[:]
    rotate(grid, direction)
    for i in range(size):
        grid[i] = [j for j in grid[i] if j != 0]
        for j in range(size):
            if j >= len(grid[i]) - 1:
                break
            if grid[i][j] == grid[i][j+1]:
                grid[i][j] += grid[i].pop(j+1)
                score += grid[i][j]
        grid[i] += [0]*(size - len(grid[i]))
    rotate(grid, complex(direction).conjugate())
    if grid != original:
        spawnNumber(grid)

try:
    print("<wasd> + [Enter]")
    spawnNumber(grid)
    display(grid)
    while not isFull(grid):
        prompt = 'Score: %d > ' % score
        direction = {'z': +1j, 'q': -1, 's': -1j, 'd': +1}.get(input(prompt).lower(), 0)
        move(grid, direction)
        display(grid)
except KeyboardInterrupt:
    print()