Halp?

.J2048
Fix 5
//The following two lines implement a predetermined test board. Tweak or abolish this as necessary.
Data(0,0,0,0,0,1,1,2,6,5,4,3,7,8,9,10,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0)->GDB1
Copy(GDB1,L1,32)
DRAW()
While 1
If getKey->K?<5
If K=2
LEFT()
End
//More slides will come once the LEFT is done.
Copy(L1+16,L1,16)
Fill(L1,16,16,0)
End
DRAW()
EndIf getKey(15)
Fix 4
Return

Lbl LEFT
0->r1
For(4)
{r1+L1}->{r1+16+L1}
1->r2
For(3)
If {r1+r2+L1}
ALEFT()
End
r2++
End
r1+4->r1
End
Return
Lbl ALEFT
0->r3
Repeat {r1+r2-r3+16+L1}??r3=r2
r3++
End
If {r1+r2+L1}={r1+r2-r3+16+L1}
{r1+r2-r3+16+L1}++
0->{r1+r2+L1}

//I know something is to be added here. What that is, I need your help to find out.

Return
ElseIf {r1+r2-r3+16+L1}=0
{r1+r2+L1}->{r1+r2-r3+16+L1}
Return
End
{r1+r2+L1}->{r1+r2-r3+17+L1}
Return
Lbl DRAW
ClrDraw
0->r1
For(4)
 and 0->r2
For(4)
If {r1/16*4+(r2/19)+L1}->r3
Text(r3<10+(r3<7)+(r3<4)*2+r2+2,r1+4,e^(r3)>Dec)
End
RectI(r2,r1,19,16)
RectI(r2+1,r1+1,17,14)
r2+19->r2
End
r1+16->r1
End
DispGraph