COOL STUF

#include <SFML/Graphics.hpp>
#include <iostream>
#include <vector>

using namespace sf;
//32px==1m
constexpr float p2m = 32.f;
using v2 = Vector2f;
v2 gravity = {0,10};

struct Entity
{
    RectangleShape body;
    float speed;
    bool jump = true;
    v2 velo = {0,0};
    v2 accel = {0,0};
    v2 movement = {0,0};
    float friction = -0.99;
    bool is_colliding(v2 pos);
    void move(v2 by);

};

std::vector<Entity> entities;

void Entity::move(v2 by)
{
    accel += by;
}

bool Entity::is_colliding(v2 pos)
{
    //v2 old = body.getPosition();
    FloatRect hbox = body.getGlobalBounds();
    //floatrect only have leftup corner
    hbox.left = pos.x - hbox.width/2.f;
    hbox.top = pos.y - hbox.height/2.f;
    //body.setPosition(pos);
    for(unsigned int i = 0; i < entities.size(); i++)
    {
        if(hbox.intersects(entities[i].body.getGlobalBounds()))
        {
            //std::cout << "a";
            //falling = false;
            //body.setPosition(old);
            return true;
        }
    }
    //body.setPosition(old);
    return false;
}

void update(Entity &player,float delta)
{
    if(sf::Keyboard::isKeyPressed(sf::Keyboard::A))
    {
        player.move({-player.speed,0.f});
    }
    if(sf::Keyboard::isKeyPressed(sf::Keyboard::D))
    {
        player.move({player.speed,0.f});
    }

    if(sf::Keyboard::isKeyPressed(sf::Keyboard::W) && player.jump == true)
    {
        player.move({0.f,-400.f});
        player.jump = false;
    }

    player.accel += gravity;

    if(player.jump == true)
    {
        player.accel += player.friction * (player.velo/p2m);
        //1
    }

    player.velo += delta * player.accel * p2m;

    v2 old_pos = player.body.getPosition();
    //std::cout << "OLD: " << old_pos.x << ":" << old_pos.y << std::endl;
    v2 new_pos = old_pos + player.velo * delta;
    //std::cout << "NEW: " << new_pos.x << ":" << new_pos.y << std::endl;

    if(!player.is_colliding({new_pos.x,old_pos.y}))
    {
        player.body.setPosition({new_pos.x,player.body.getPosition().y});
    }
    else
    {
        player.velo.x = 0.f;
    }

    if(!player.is_colliding({old_pos.x,new_pos.y}))
    {
        player.body.setPosition({player.body.getPosition().x,new_pos.y});
        player.jump = false;
    }
    else
    {
        player.jump = true;
        player.velo.y = 0.f;
    }

    player.accel = {0,0};
}

int main()
{

    float width = 512;
    float height = 288;
    sf::RenderWindow window(sf::VideoMode(width,height), "SFML works!");
    window.setFramerateLimit(60);
    Entity ground;
    ground.body.setSize(sf::Vector2f(320.f,64.f));
    ground.body.setOrigin(sf::Vector2f(ground.body.getSize().x*0.5,ground.body.getSize().y*0.5));
    ground.body.setPosition(sf::Vector2f(0.5*width,height));
    entities.push_back(ground);
    Entity player;
    player.speed = 68.f;
   // player.falling = false;
    player.body.setSize(sf::Vector2f(32.f,32.f));
    player.body.setOrigin(sf::Vector2f(player.body.getSize().x*0.5,player.body.getSize().y*0.5));
    player.body.setPosition(sf::Vector2f(width*0.5,height-ground.body.getSize().y));

    sf::Clock clock;
    while (window.isOpen())
    {
        sf::Event event;
        sf::Time time = clock.restart();
        while (window.pollEvent(event))
        {
            if (event.type == sf::Event::Closed)
                window.close();
        }

        float loopTime = time.asSeconds();
        //std::cout << loopTime << std::endl;
        update(player,loopTime);
        window.clear();
        window.draw(ground.body);
        window.draw(player.body);
        window.display();
    }

    return 0;
}