Commit 7ff96f95 authored by Mauro Aranda's avatar Mauro Aranda Committed by Eli Zaretskii
Browse files

Fix pong collision detection

* lisp/play/pong.el (pong-update-game): If the ball hit the bat where
bats are positioned, draw again the bat cell in the old ball
position.  (Bug#20579).
Also, avoid changing the direction of the ball right after hitting the
bats, and improve the collision detection against the borders.
parent e503e9d3
Pipeline #2804 failed with stage
in 90 minutes and 2 seconds
......@@ -349,46 +349,61 @@ detection and checks if a player scores."
(let ((old-x pong-x)
(old-y pong-y))
;; Erase the last ball position.
(when (and (> old-y 0)
(< old-y (- pong-height 1)))
;; If the ball hit the bat in the column where bats are positioned,
;; and therefore changed its x direction, draw again the bat cell.
(if (or (and (= old-x 2) (< 0 pong-xx))
(and (= old-x (- pong-width 3)) (> 0 pong-xx)))
(gamegrid-set-cell old-x old-y pong-bat)
(gamegrid-set-cell old-x old-y pong-blank)))
;; Update the ball position.
(setq pong-x (+ pong-x pong-xx))
(setq pong-y (+ pong-y pong-yy))
(if (and (> old-y 0)
(< old-y (- pong-height 1)))
(gamegrid-set-cell old-x old-y pong-blank))
;; If the ball would go out of bounds, put it against the border.
(cond
((<= (+ pong-y pong-yy) 0)
(setq pong-yy (- pong-yy))
(setq pong-y 1))
((>= (+ pong-y pong-yy) (- pong-height 1))
(setq pong-yy (- pong-yy))
(setq pong-y (- pong-height 2)))
(t
(setq pong-y (+ pong-y pong-yy))
;; Check if the ball is against the border now,
;; and change the y direction if it is.
(when (or (<= pong-y 1) (>= pong-y (- pong-height 2)))
(setq pong-yy (- pong-yy)))))
;; Draw the ball in its new position.
(if (and (> pong-y 0)
(< pong-y (- pong-height 1)))
(gamegrid-set-cell pong-x pong-y pong-ball))
;; Hit bat, score a goal, or nothing.
(cond
((or (= pong-x 3) (= pong-x 2))
(if (and (>= pong-y pong-bat-player1)
(< pong-y (+ pong-bat-player1 pong-bat-width)))
(and
(setq pong-yy (+ pong-yy
(cond
((= pong-y pong-bat-player1) -1)
((= pong-y (1+ pong-bat-player1)) 0)
(t 1))))
(setq pong-xx (- pong-xx)))))
((or (= pong-x (- pong-width 4)) (= pong-x (- pong-width 3)))
(if (and (>= pong-y pong-bat-player2)
(< pong-y (+ pong-bat-player2 pong-bat-width)))
(and
(setq pong-yy (+ pong-yy
(cond
((= pong-y pong-bat-player2) -1)
((= pong-y (1+ pong-bat-player2)) 0)
(t 1))))
(setq pong-xx (- pong-xx)))))
((<= pong-y 1)
(setq pong-yy (- pong-yy)))
((>= pong-y (- pong-height 2))
(setq pong-yy (- pong-yy)))
((and (or (= pong-x 3) (= pong-x 2))
(> 0 pong-xx) ; Collide with the bat if headed towards it.
(>= pong-y pong-bat-player1)
(< pong-y (+ pong-bat-player1 pong-bat-width)))
(setq pong-yy (+ pong-yy
(cond
((= pong-y pong-bat-player1) -1)
((= pong-y (1+ pong-bat-player1)) 0)
(t 1))))
(setq pong-xx (- pong-xx)))
((and (or (= pong-x (- pong-width 4)) (= pong-x (- pong-width 3)))
(< 0 pong-xx) ; Collide with the bat if headed towards it.
(>= pong-y pong-bat-player2)
(< pong-y (+ pong-bat-player2 pong-bat-width)))
(setq pong-yy (+ pong-yy
(cond
((= pong-y pong-bat-player2) -1)
((= pong-y (1+ pong-bat-player2)) 0)
(t 1))))
(setq pong-xx (- pong-xx)))
((< pong-x 1)
(setq pong-score-player2 (1+ pong-score-player2))
......
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