GGJ2013 'Feelings' physics

    public class Player
    {
        public static float MINACCEL = 250;//120;
        public static float MINSPEED = 40;
        public static float MAXSPEED = 400;
        public static float RUNMAXSPEED = 1000;
        public static float DECELERATION = 12f; //Divides by (1 + DEC)
        public static float ACCELERATION = 200;
        public static float RUNACCELERATION = 500;
        public static float VERTDEC = 3f; //Vertical deceleration: divides by (1 + DEC)
        public static float MINVERTSPEED = 200f;
        public static float JUMPFORCE = 550f;


        public float x = 600;
        public float y = 0;
        public float velocityX = 0;
        public float velocityY = 0;
        public float width = 0;
        public float height = 0;
    public bool isJumping = true;
    public bool canjump = false;

        public Sprite sprite;

[...]

        public void Update(GameTime gameTime)
        {
            float seconds=(float)gameTime.ElapsedGameTime.TotalSeconds;

            //Update width/height
            this.width = this.sprite.GetImage().Width;
            this.height = this.sprite.GetImage().Height;

            //Calculate position and check for collision
            float targetX = x + velocityX * seconds;
            float targetY = y + velocityY * seconds;


            if (targetX < 0) targetX = 0;
            if (targetX + width > Main.LEVEL_EDGE_X) targetX = Main.LEVEL_EDGE_X - width;


            if(Util.CheckCollision(targetX+width-1, targetY+4, 1, height-8, // collision for right side
                Main.core.x, Main.core.y, Main.core.sprite.GetImage().Width, Main.core.sprite.GetImage().Height))// right side
            {
                if(velocityX>-1){
                    targetX = x;
                }
            }

            if(Util.CheckCollision(targetX, targetY+4, 1, height-8, // collision for left side
                Main.core.x, Main.core.y, Main.core.sprite.GetImage().Width, Main.core.sprite.GetImage().Height))
                {
                    if(velocityX<0){
                        targetX = x;
                    }
                }

           if( (Util.CheckCollision(targetX+2, targetY+height, width-4, 1, // down check
                  Main.core.x, Main.core.y, Main.core.sprite.GetImage().Width, Main.core.sprite.GetImage().Height)) || (targetY+height>Main.GROUNDY))// core collision
            {
                if(velocityY>0){
                    while( (Util.CheckCollision(targetX+2, targetY+height, width-4, 1, // down check
                      Main.core.x, Main.core.y, Main.core.sprite.GetImage().Width, Main.core.sprite.GetImage().Height)) || (targetY+height>Main.GROUNDY) )
                    {
                        targetY--;
                    }


                    targetY++;
                    velocityY = 0;
                    isJumping = false;
                    canjump = true;
                }
           } else
           {
                isJumping = true;
                canjump = false;
           }

            if(isJumping){ //handle jumping
                velocityY += 1300 * seconds;
                y+=velocityY*seconds;
            }

           //Update position
            x = targetX;
            y = targetY;

            //Update sprite

            //Animations
            if (this.sprite.currentAnimation != "default" && this.velocityX == 0 && this.velocityY == 0) this.sprite.ChangeAnimation("default");
            else if (this.sprite.currentAnimation != "jumping" && (this.velocityY < 0 || this.velocityY > 0)) this.sprite.ChangeAnimation("jumping");
            else if (this.sprite.currentAnimation != "running" && (this.velocityX < 0 || this.velocityX > 0) && this.velocityY == 0) this.sprite.ChangeAnimation("running");

            //Flip and position
            if (velocityX > 0) this.sprite.isFlipped = Microsoft.Xna.Framework.Graphics.SpriteEffects.None; //Don't flip - face right
            else if (velocityX < 0) this.sprite.isFlipped = Microsoft.Xna.Framework.Graphics.SpriteEffects.FlipHorizontally; //Flip - face left
            this.sprite.SetPosition(x, y); //Set position to player position
        }

        public void Jump()
        {
            Audio.PlaySound("jump");
            this.velocityY = -JUMPFORCE;
        }

    }

-------------------------

    public static class Input
    {
        public static void Update(GameTime gameTime)
        {
            oldState = newState;
            newState = Keyboard.GetState();

            if (Main.gameState == Main.GameState.Playing)
            {
                //===================PLAYING==================
                //------------------Move left/right--------------------
                //Acceleration stuff
                float velocityMod = 0;
                if (newState.IsKeyDown(Keys.LeftShift) || newState.IsKeyDown(Keys.RightShift)) //Running
                {
                    if (newState.IsKeyDown(Keys.Left)) velocityMod = -Player.RUNACCELERATION;
                    if (newState.IsKeyDown(Keys.Right)) velocityMod = Player.RUNACCELERATION;
                }
                else //Normal speed
                {
                    if (newState.IsKeyDown(Keys.Left)) velocityMod = -Player.ACCELERATION;
                    if (newState.IsKeyDown(Keys.Right)) velocityMod = Player.ACCELERATION;
                }

                if (Main.player.velocityX < Player.MINACCEL && Main.player.velocityX > -Player.MINACCEL && velocityMod > 0) //Quick start up - right
                {
                    Main.player.velocityX = Player.MINACCEL;
                }
                else if (Main.player.velocityX > -Player.MINACCEL && Main.player.velocityX < Player.MINACCEL && velocityMod < 0) //Quick start up - left
                {
                    Main.player.velocityX = -Player.MINACCEL;
                }
                else //Normal acceleration
                {
                    Main.player.velocityX += velocityMod * (float)gameTime.ElapsedGameTime.TotalSeconds;
                }

                //Decelerate if not pushing direction or pushing opposite direction
                if (velocityMod == 0 || (velocityMod < 0 && Main.player.velocityX > 0) || (velocityMod > 0 && Main.player.velocityX < 0))
                {
                    Main.player.velocityX = Main.player.velocityX / (1 + (Player.DECELERATION * (float)gameTime.ElapsedGameTime.TotalSeconds));
                }

                //Stop the player if below min speed
                if ((Main.player.velocityX < Player.MINSPEED && Main.player.velocityX > 0) || (Main.player.velocityX > -Player.MINSPEED && Main.player.velocityX < 0))
                {
                    Main.player.velocityX = 0;
                }

                //Fix speed if over limit
                float maxSpeed = Player.MAXSPEED;
                if (newState.IsKeyDown(Keys.RightShift) || newState.IsKeyDown(Keys.LeftShift)) maxSpeed = Player.RUNMAXSPEED;
                if (Main.player.velocityX > maxSpeed) Main.player.velocityX = maxSpeed;
                if (Main.player.velocityX < -maxSpeed) Main.player.velocityX = -maxSpeed;

                //----------------------------Jump-----------------
                if (KeyPressed(Keys.Space) || KeyPressed(Keys.Z) || KeyPressed(Keys.Up))
                {
                    if (Main.player.canjump)
                    {
                        Main.player.Jump();
                        Main.player.isJumping = true;
                        Main.player.canjump = false;
                    }
                }
[...]
            }
[...]
        }
[...]
    }