Jumpy box

#!/usr/bin/env python

import pygame
from pygame.locals import *
import sys

pygame.init()

size = width, height = 800, 600

black = 0, 0, 0
white = 255, 255, 255

screen = pygame.display.set_mode(size)

clock = pygame.time.Clock()

class Entity:
    def __init__(self):
        self.x = 0
        self.y = 0
        self.xv = 0
        self.yv = 0
        self.h = 0
        self.w = 0
        self.rect = pygame.Rect((0, 0, 0, 0))
        self.onGround = False

    def set_pos(self, x, y):
        self.x = x
        self.y = y
        self.onGround = False
        if self.y < 200:
            self.onGround = True
            self.y = 200
        self.rect.x = x
        self.rect.y = y

    def set_vel(self, x, y):
        self.xv = x
        self.yv = y

    def set_size(self, w, h):
        self.w = w
        self.t = w
        self.h = h
        self.rect.w = w
        self.rect.h = h

    def move_x(self):
        self.set_pos(self.x + self.xv, self.y)

    def move_y(self):
        if self.onGround:
            self.set_pos(self.x, self.y)
        else:
            self.set_pos(self.x, self.y + self.yv)
        if self.yv > -5: self.yv-=1

    def colliding(self, rect):
        self.coll = self.rect.colliderect(rect)
        if self.coll:
            self.onGround = True
        return self.coll

    def jump(self):
        if self.onGround:
            self.yv = 15

    def drawrect(self):
        return pygame.Rect((self.x, 600 - self.y, self.w, self.h))

# Plr = pygame.Rect(5, 5, 150, 150)

Plr = Entity()
Plr.set_pos(200, 300)
Plr.set_size(64, 64)

box = Entity()
box.set_pos(200, 200)
box.set_size(64, 64)

while True:
    for event in pygame.event.get():
        if event.type == pygame.QUIT:
            sys.exit()
        elif event.type == pygame.KEYUP:
            if event.key == K_ESCAPE:
                sys.exit()

    keydown = pygame.key.get_pressed()
    if keydown[K_LEFT]:
        Plr.xv = -5
    elif keydown[K_RIGHT]:
        Plr.xv = 5
    else:
        Plr.xv = 0
    if keydown[K_SPACE]:
        Plr.jump()

    Plr.move_x()

    if Plr.colliding(box.rect):
        if Plr.xv < 0:
            Plr.x = box.x + box.t
            Plr.xv = 0
        if Plr.xv > 0:
            Plr.x = box.x - Plr.w
            Plr.xv = 0

    Plr.move_y()

    if Plr.colliding(box.rect):
        if Plr.yv < 0:
            Plr.y = box.y + box.t
            Plr.yv = 0
        if Plr.yv > 0:
            Plr.onGround = True
            Plr.y = box.y - Plr.h
            Plr.yv = 0

    screen.fill(black)

    pygame.draw.rect(screen, white, Plr.drawrect())
    pygame.draw.rect(screen, white, box.drawrect())

    pygame.display.flip()
    clock.tick(60)