From f8cc4a748bb8b6431a1023a876745b1bb473eb19 Mon Sep 17 00:00:00 2001
From: Gene Pasquet <dev@etenil.net>
Date: Wed, 8 Apr 2026 00:30:11 +0100
Subject: Support entity groups

---
 demo/topdown.scm | 49 +++++++++++++++++++++++++++++--------------------
 1 file changed, 29 insertions(+), 20 deletions(-)

(limited to 'demo/topdown.scm')

diff --git a/demo/topdown.scm b/demo/topdown.scm
index 2b3c208..7e5bd62 100644
--- a/demo/topdown.scm
+++ b/demo/topdown.scm
@@ -1,5 +1,6 @@
 (import scheme
         (chicken base)
+        (only srfi-197 chain)
         (prefix sdl2 "sdl2:")
         (prefix sdl2-ttf "ttf:")
         (prefix sdl2-image "img:")
@@ -13,36 +14,44 @@
         downstroke-entity
         downstroke-scene-loader)
 
+(define (make-player)
+  (list #:type 'player
+        #:x 100 #:y 100
+        #:width 16 #:height 16
+        #:vx 0 #:vy 0
+        #:gravity? #f
+        #:tile-id 1 #:tags '(player)))
+
+(define (input->velocity input)
+  (values (+ (if (input-held? input 'left)  -3 0)
+             (if (input-held? input 'right)  3 0))
+          (+ (if (input-held? input 'up)    -3 0)
+             (if (input-held? input 'down)   3 0))))
+
+(define (update-player player input tm)
+  (receive (dx dy) (input->velocity input)
+    (chain player
+           (entity-set _ #:vx dx)
+           (entity-set _ #:vy dy)
+           (apply-velocity-x _)
+           (resolve-tile-collisions-x _ tm)
+           (apply-velocity-y _)
+           (resolve-tile-collisions-y _ tm))))
+
 (define *game*
   (make-game
     title: "Demo: Top-down Explorer" width: 600 height: 400
 
     create: (lambda (game)
-      (let* ((scene  (game-load-scene! game "demo/assets/level-0.tmx"))
-             (player (list #:type 'player
-                           #:x 100 #:y 100
-                           #:width 16 #:height 16
-                           #:vx 0 #:vy 0
-                           #:gravity? #f
-                           #:tile-id 1
-                           #:tags '(player)))
-             (_ (scene-add-entity scene player)))
+      (let ((scene (game-load-scene! game "demo/assets/level-0.tmx")))
+        (scene-add-entity scene (make-player))
         (scene-camera-target-set! scene 'player)))
 
     update: (lambda (game dt)
       (let* ((input  (game-input game))
              (scene  (game-scene game))
-             (tm     (scene-tilemap scene))
-             (player (car (scene-entities scene)))
-             (dx (+ (if (input-held? input 'left)  -3 0)
-                    (if (input-held? input 'right)  3 0)))
-             (dy (+ (if (input-held? input 'up)    -3 0)
-                    (if (input-held? input 'down)    3 0)))
-             (player (entity-set (entity-set player #:vx dx) #:vy dy))
-             (player (apply-velocity-x player))
-             (player (resolve-tile-collisions-x player tm))
-             (player (apply-velocity-y player))
-             (player (resolve-tile-collisions-y player tm)))
+             (player (update-player (car (scene-entities scene))
+                                    input (scene-tilemap scene))))
         (scene-entities-set! scene (list player))))))
 
 (game-run! *game*)
-- 
cgit v1.2.3