platform | check points | gml

objPlayer Create

// add player checkpoint variables:
checkpoint_x = xstart;
checkpoint_y = ystart;

wherever player needs to restart:

// restart player at most recent checkpoint:
x = checkpoint_x;
y = checkpoint_y;

objPlayer Collision Event with objCheckpoint

checkpoint_x = x;
checkpoint_y = y;
with(other){
  instance_destroy();	
}