how to create a simple gravity system like in platform games??

thanks for the help

Something like this maybe ???

Code:

---

  vec_set (temp, my.x); 
temp.z -= 10000; 
trace_mode = ignore_me + ignore_passable + use_box+activate_sonar; 		
my.skill30 = trace (my.x, temp)-5;
if(result <= 0 ) 

//place player on ground 
vec_set(VecFrom,my.x); 
vec_set(VecTo,my.x);
VecTo.z -= 30* time; // place player on floor 
						

---

what is "temp"???

line 1.The vector to be traced
Line 2. The distance to be traced
line 3. The trace mode used
Line 4. The actual trace stored as my.skill30 to use later if need be
Line 5, 6. comparisons
Line 7. the speed and force of the placement (gravity)