Hello physics

[dajan]

This is kind of hello world program for some basic 2D ball physics (acceleration, friction, gravity, inelastic collision) implemented with the aim of using the fewest code lines and variables possible. This of course limits it's fidelity.

Hit W, S, A, D keys to accelerate the ball.

Code: QB64: [Select]

1. SCREEN 12
2. DO
3.     CLS
4.     vx = ((x < 20 OR x > 620) * 1.9 + 1) * (vx - _KEYDOWN(ASC("d")) + _KEYDOWN(ASC("a"))) * 0.99
5.     vy = ((y < 20 OR y > 460) * 1.9 + 1) * (vy - _KEYDOWN(ASC("s")) + _KEYDOWN(ASC("w"))) * 0.99 + 10 / 60
6.     x = x + vx - (x < 20) + (x > 620)
7.     y = y + vy - (y < 20) + (y > 460)
8.     CIRCLE (x, y), 20, 7
9.     _DISPLAY
10.     _LIMIT 60
11. LOOP UNTIL _KEYDOWN(27)
12.  

/Edit: further code enhancements collected

Let's keep on concise coding, now sacrificing 5 more lines to build some game logic into the "engine":

Code: QB64: [Select]

1. SCREEN 12
2. t = TIMER + 90
3. DO
4.     CLS
5.     vx = ((x < 20 OR x > 620) * 1.9 + 1) * (vx + (x < 200 AND y > 250) * _KEYDOWN(ASC("d")) / 2 - (y > 250) * _KEYDOWN(ASC("a")) / 2) * 0.99
6.     vy = ((y > 460) * 1.9 + 1) * (vy + (x < 200 AND y > 250) * _KEYDOWN(ASC("s")) / 2 - (x < 200 AND y > 250) * _KEYDOWN(ASC("w")) / 2) * 0.99 + 0.17
7.     x = x + vx - (x < 20) + (x > 620)
8.     y = y + vy + (y > 460)
9.     p = ((p = 0) + 2 * ((p = 1 OR p = 2))) * (y > 200 AND y < 250 AND ABS(580 - (x - vx / vy * (y - 200))) < 30 AND vy > 0)
10.     s = s - (p = 1)
11.     PRINT "Time:"; _ROUND(t - TIMER), "Score: "; s
12.     DRAW "BM0,250C2dR200D230BM530,200C4R100C" + STR$(7 + p) + "TA-15D100H15D20H15D20H15D20TA15U100"
13.     CIRCLE (x, y), 20, 6
14.     _DISPLAY
15.     _LIMIT 60
16. LOOP UNTIL _KEYDOWN(27) OR (TIMER > t AND y > 250)
17.  

Time to add some bit more advanced features. Ball-rim collisions would be nice:

Code: QB64: [Select]

1. SCREEN 12
2. t = TIMER + 90
3. DO
4.     CLS
5.     vx = ((x < 25 OR x > 615) * 1.9 + 1) * (vx + (x < 200 AND y > 250) * _KEYDOWN(ASC("d")) - (y > 250) * _KEYDOWN(ASC("a"))) * 0.987
6.     vy = ((y > 455) * 1.9 + 1) * (vy + (x < 200 AND y > 250) * _KEYDOWN(ASC("s")) - (x < 200 AND y > 250) * _KEYDOWN(ASC("w"))) * 0.987 + 0.327
7.     vd = SQR(vx ^ 2 + vy ^ 2)
8.     rx(1) = 520: ry(1) = 200: rx(2) = 620: ry(2) = 200 'rim position
9.     FOR i = 1 TO 2
10.         dd = SQR((rx(i) - x) ^ 2 + (ry(i) - y) ^ 2)
11.         nx = ((vx * (rx(i) - x) + vy * (ry(i) - y)) * -vx - (vx * (ry(i) - y) - vy * (rx(i) - x)) * -vy) / vd / dd * 0.9
12.         ny = ((vx * (ry(i) - y) - vy * (rx(i) - x)) * -vx + (vx * (rx(i) - x) + vy * (ry(i) - y)) * -vy) / vd / dd * 0.9
13.         vx = (dd < 25) * -nx + (dd >= 25) * -vx
14.         vy = (dd < 25) * -ny + (dd >= 25) * -vy
15.     NEXT i
16.     x = x + vx - (x < 25) * 2 + (x > 615) * 2
17.     y = y + vy + (y > 455) * 2
18.     p = ((p = 0) + 2 * (p <> 0)) * (y > 210 AND y < 240 AND ABS(570 - (x - vx / vy * (y - 200))) < 25) * ((vy < 0) * 2 + 1)
19.     s = s - (p = 1) + (p = -1)
20.     net = -((x > 500 AND x < 620 AND y > 200 AND y < 300) AND (p > 0 OR ABS(net) > 0)) * _ROUND((x - 570) - ((x > 570) * 2 + 1) * (y - 250) * 0.3) * 0.9
21.     PRINT "Time:"; _ROUND(t - TIMER), "Score: "; s
22.     FOR i = 1 TO 20: CIRCLE (x, y), i * 25 / 20, 6: NEXT
23.     DRAW "BM0,250C2R200D230BM520,200C4R119D1L119D1R119D20H20C7M-" + STR$(30 - net) + ",100M-10,-15M-10,15M-10,-15M-10,15M-" + STR$(30 + net) + ",-100"
24.     _DISPLAY
25.     _LIMIT 60
26. LOOP UNTIL _KEYDOWN(27) OR (TIMER > t AND y > 250)
27.  

[romichess]

Thank you. This is the perfect example to get started!

[OldMoses]

That was fun, who knew you could get so much amusement out of 11 lines of code?

[bplus]

I am betting the ball is accelerated more than once with each key press.

[dajan]

Bplus, indeed, the ball keeps accelerating as long as you hold the key.

OldMoses,  I wondered if it can be squeezed under 10 lines, without chaining commands of course, but probbably not.

[DANILIN]

Code: [Select]

CIRCLE (x, y), 20, 7
powerful washer

Code: [Select]

FOR i = 1 TO 10: CIRCLE (x, y), 10 + i, 5: NEXT

[STxAxTIC]

I really liked this demo. Crammed to pounds of physics in a 5 pound bag, no doubt.

[Qwerkey]

I am in agreement.  Rather pleasing for seemingly concise code.

[TempodiBasic]

yeah!
welcome physics, where are  you form?
This fine example let me remember this  https://en.wikipedia.org/wiki/La_Linea_(TV_series)

[dajan]

Ok guys, glad you liked it. Let's keep on concise coding, now sacrificing 5 more lines to build some game logic into the "engine":

Try to guess the game rules on your own :o)

Code: QB64: [Select]

1. SCREEN 12
2. t = TIMER + 90
3. DO
4.     CLS
5.     vx = ((x < 20 OR x > 620) * 1.9 + 1) * (vx + (x < 200 AND y > 250) * _KEYDOWN(ASC("d")) / 2 - (y > 250) * _KEYDOWN(ASC("a")) / 2) * 0.99
6.     vy = ((y > 460) * 1.9 + 1) * (vy + (x < 200 AND y > 250) * _KEYDOWN(ASC("s")) / 2 - (x < 200 AND y > 250) * _KEYDOWN(ASC("w")) / 2) * 0.99 + 0.17
7.     x = x + vx - (x < 20) + (x > 620)
8.     y = y + vy + (y > 460)
9.     p = ((p = 0) + 2 * ((p = 1 OR p = 2))) * (y > 200 AND y < 250 AND ABS(580 - (x - vx / vy * (y - 200))) < 30 AND vy > 0)
10.     s = s - (p = 1)
11.     PRINT "Time:"; _ROUND(t - TIMER), "Score: "; s
12.     DRAW "BM0,250C2dR200D230BM530,200C4R100C" + STR$(7 + p) + "TA-15D100H15D20H15D20H15D20TA15U100"
13.     CIRCLE (x, y), 20, 6
14.     _DISPLAY
15.     _LIMIT 60
16. LOOP UNTIL _KEYDOWN(27) OR (TIMER > t AND y > 250)
17.  

[dajan]

TempodiBasic I'm from Slovakia, if you are asking me. I remember LaLinea, liked to watch it on TV, it has its cool minimalistic style and was pretty funny.

[bplus]

Hi dajan,

Is the game of HORSE known in Slovakia?

[FellippeHeitor]

That's SO cool!

[dajan]

Hi bplus, no, I didn't know of HORSE bsaketball mod. Actually it took me 1 wikipedia and 2 YT videos to understand what is that about :o)

[dajan]

FellippeHeitor, thanks!