For inspiration - with source ;-)
GuiParas equ "Birds", w500, h320, b none
include \masm32\MasmBasic\Res\MbGui.asm
SetGlobals SDWORD bird1X, bird1Y, bird2X, bird2Y, d1y, d2y
mov eax, GuiHeight
sar eax, 1
sub eax, 30
mov bird1Y, eax
add eax, 60
mov bird2Y, eax
Event Paint
GuiImage "sky.png", fit
GuiImage "tweety.gif", bird1X, bird1Y, 60, 60
GuiImage "tweety.gif", bird2X, bird2Y
Event Timer
sub bird1X, 5
.if bird1X<-60
m2m bird1X, GuiWidth
.endif
sub bird2X, 4
.if bird2X<-60
m2m bird2X, GuiWidth
.endif
sub Rand(11), 5
add eax, d1y
add bird1Y, eax
.if bird1Y<20
dec d1y
.elseif bird1Y>250
inc d1y
.endif
sar eax, 1
inc eax
.if bird2Y<20
dec d2y
.elseif bird2Y>250
inc d2y
.endif
add eax, d2y
sub bird2Y, eax
GuiCls
GuiEnd