The Adventures of Tokk Project Report Raphael Leon 31 may 2014 | Page 11

These variables tell the character what keyboard buttons will effect its
movement. This states that the “right arrow” moves right (it is equal to +1), the
“left arrow” moves left (it is equal to -1) and the “space bar” jumps.
// react to imputs
move = key_left + key_right;
hsp = move * movespeed;

As only one key is usually pressed “move” equals “key_left” + “key_right”
which means “move” will either be +1 or -1 (or 0 if both or neither is pressed).
Our horizontal speed, hsp, is equal to “-1 X 4” if the left key is pressed causing the
character to move left and the opposite is true if the right key is pressed.
if (vsp < 10) vsp += grav;
if (place_meeting (x, y+1, obj_wall))
{
vsp = key_jump * -jumpspeed
}

The first line of code makes gravity affect the player. The next line states
that if the character is grounded (“x, y+1, obj_wall” asks the computer whether
one pixel below the character is a wall), vertical speed, vsp, can equal +1 when
the space bar is pressed times by -7 (jumpspeed) resulting in a jump.
// horizontal collision
if (place_meeting (x+hsp, y, obj_wall))
{
while(!place_meeting (x+sign(hsp) ,y, obj_wall))
{
x += sign(hsp);
}
hsp = 0;
} x +=hsp;

The first three lines tell the character to see whether it is about to collide
with the object_wall and if it is to prepare for a collision when it does. The last
line (x +=hsp;) means that the engine will add our horizontal speed to the Y
coordinate.
// vertical collision
if (place_meeting (x, y+vsp, obj_wall))
{
while(!place_meeting (x, y+sign(vsp), obj_wall))
{
y += sign(vsp);
} vsp = 0;
} y += vsp;

The first three lines tell the character to see whether it is about to collide
with the object_wall and if it is, to prepare for a collision when it does. The last

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