Here is a code:

Code: QB64: [Select]

1. _TITLE "A Promising Game!"
2. SCREEN _NEWIMAGE(800, 600, 32)
3. COLOR , _RGB32(211, 211, 211)
4. CLS
5. DIM SHARED x AS INTEGER
6. DIM SHARED y AS INTEGER
7. DIM SHARED gravity AS SINGLE
8. DIM SHARED y_change AS SINGLE
9. restart:
10. x = 200
11. y = 200
12. gravity = 9.8
13. CLS
14. DO
15.     CLS
16.     makechar
17.     k$ = UCASE$(INKEY$)
18.     IF _KEYDOWN(18432) AND NOT y_change > 50 THEN
19.         y = y - 25
20.         y_change = y_change + 1
21.         y = y + gravity
22.     ELSEIF _KEYDOWN(20480) AND NOT y_change > 50 THEN
23.         y = y + 25
24.         y_change = y_change + 1
25.         y = y + gravity
26.     ELSEIF _KEYDOWN(19200) THEN
27.         x = x - 10
28.     ELSEIF _KEYDOWN(19712) THEN
29.         x = x + 10
30.     END IF
31.     y = y + gravity
32.     'Blocks
33.     'LINE (100, 400)-STEP(200, 50), _RGB32(255, 83, 33), BF
34.     'IF collision%(x, y, 20, 20, 100, 400, 200, 50) THEN
35.     '    y = oldy
36.     '    y_change = 0
37.     '    gravity = 0
38.     'ELSE
39.     '    gravity = 9.8
40.     '    oldy = y
41.     'END IF
42.     makeobs 100, 400
43.     LINE (500, 400)-STEP(200, 50), _RGB32(127, 255, 127), BF
44.     IF collision%(x, y, 20, 20, 500, 400, 200, 50) THEN
45.         CLS
46.         _PRINTSTRING (300, 300), "LEVEL 1 COMPLETE!"
47.         END
48.     END IF
49.     IF y > 700 THEN GOTO restart
50.  
51.     _DISPLAY
52.     _LIMIT 60
53. LOOP
54.  
55. SUB makechar
56.     CIRCLE (x, y), 20, _RGB32(100, 150, 255)
57.     PAINT (x, y), _RGB32(100, 150, 255), _RGB32(100, 150, 255)
58. END SUB
59.  
60. FUNCTION collision% (b1x, b1y, b1w, b1h, b2x, b2y, b2w, b2h)
61.     IF (b1y + b1h < b2y) OR (b1y > b2y + b2h) OR (b1x > b2x + b2w) OR (b1x + b1w < b2x) THEN
62.         collision% = 0
63.     ELSE
64.         collision% = 1
65.     END IF
66. END FUNCTION
67.  
68. SUB makeobs (bx, by)
69.     LINE (bx, by)-STEP(200, 50), _RGB32(255, 150, 100), BF
70.     IF collision%(x, y, 20, 20, bx, by, 200, 50) THEN
71.         y = oldy
72.         gravity = 0
73.         y_change = 0
74.     ELSE
75.         oldy = y
76.         gravity = 9.8
77.     END IF
78. END SUB
79.  

What is the bug that brings the player to it's initial position?

It’s because the _KEYDOWN check gimp freejobalert notepad++  is in an ELSEIF statement.  Make all those become independent IF checks instead.

Thanks Both of you for this. I was also facing the same and happened to find this has already been answered.

Regards,
Amanda