From 98645c73173880d72a12fbede5748c28214e7846 Mon Sep 17 00:00:00 2001
From: Thomas White <taw@physics.org>
Date: Sun, 20 Sep 2020 12:16:30 +0200
Subject: Separate x and y velocities

Gravity and walking need to be handled differently
---
 heyllama.scm | 76 ++++++++++++++++++++++++++++++++++++++++--------------------
 1 file changed, 51 insertions(+), 25 deletions(-)

diff --git a/heyllama.scm b/heyllama.scm
index da6c927..6a71a0d 100644
--- a/heyllama.scm
+++ b/heyllama.scm
@@ -20,9 +20,9 @@
   (draw-offset #:init-keyword #:draw-offset
                #:getter get-draw-offset)
 
-  (vel #:init-value #v(0.0 0.0)
-       #:getter get-vel
-       #:setter set-vel!)
+  (y-vel #:init-value 0.0
+       #:getter get-y-vel
+       #:setter set-y-vel!)
 
   (face-direction
    #:init-keyword #:face-dir
@@ -135,27 +135,53 @@
 
 (define (update tstep)
 
-  (when (key-pressed? 'right)
-    (set-face-direction! llama 1)
-    (vec2-add! (get-pos llama) #v((* tstep 0.2) 0))
-    (set-animation-step! llama
-                         (floor-remainder
-                          (+ (get-animation-step llama) -1)
-                          16)))
-
-  (when (key-pressed? 'left)
-    (set-face-direction! llama -1)
-    (vec2-add! (get-pos llama) #v((* tstep -0.2) 0))
-    (set-animation-step! llama
-                         (floor-remainder
-                          (- (get-animation-step llama) 1)
-                          16)))
-
-  (vec2-add! (get-pos llama) #v(0.0 -1.0))
-  (grid-move grid 'llama (get-pos llama) (lambda (a b)
-                                           (if (eq? a 'llama)
-                                               slide
-                                               #f)))
+  (let ((x-vel 0.0))
+
+    (define (slide-llama-only a b)
+       (if (eq? a 'llama) slide #f))
+
+    (when (key-pressed? 'right)
+      (set-face-direction! llama 1)
+      (set! x-vel 1.0)
+      (set-animation-step! llama
+                           (floor-remainder
+                            (+ (get-animation-step llama) -1)
+                            16)))
+
+    (when (key-pressed? 'left)
+      (set-face-direction! llama -1)
+      (set! x-vel -1.0)
+      (set-animation-step! llama
+                           (floor-remainder
+                            (- (get-animation-step llama) 1)
+                            16)))
+
+    (vec2-add! (get-pos llama)
+               #v((* x-vel tstep 0.2) 0.0))
+
+    (grid-move grid
+               'llama
+               (get-pos llama)
+               slide-llama-only))
+
+  ;; Gravity
+  (define (slide-llama-only-and-zero-yvel a b)
+    (if (eq? a 'llama)
+        (lambda (item item-rect other other-rect goal)
+          (set-y-vel! llama 0.0)
+          (slide item item-rect other other-rect goal))
+        #f))
+
+  (set-y-vel! llama
+              (- (get-y-vel llama) 0.4))
+
+  (vec2-add! (get-pos llama)
+             #v(0.0 (get-y-vel llama)))
+
+  (grid-move grid
+             'llama
+             (get-pos llama)
+             slide-llama-only-and-zero-yvel)
 
   ;; Ensure llama is near centre of screen
   (let ((fovea (make-rect 150.0 150.0 350.0 350.0))
@@ -169,7 +195,7 @@
     ((q) (abort-game))
     ((f1) (set! show-hitboxes (not show-hitboxes)))
     ((space) (unless repeat?
-               (set-vel! llama #v(0.0 15.0))))))
+               (set-y-vel! llama 8.0)))))
 
 
 (run-game #:window-title "Hey Llama!"
-- 
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