1 files changed, 139 insertions, 0 deletions
diff --git a/demo/tweens.scm b/demo/tweens.scm
new file mode 100644
index 0000000..e9e40f3
--- /dev/null
+++ b/demo/tweens.scm
@@ -0,0 +1,139 @@
+(import scheme
+        (chicken base)
+        (only srfi-1 iota map)
+        (prefix sdl2 "sdl2:")
+        (prefix sdl2-ttf "ttf:")
+        (prefix sdl2-image "img:")
+        downstroke-engine
+        downstroke-world
+        downstroke-tilemap
+        downstroke-renderer
+        downstroke-physics
+        downstroke-entity
+        downstroke-tween
+        downstroke-scene-loader)
+
+;; One row per easing symbol: #(entity tween left-x right-x ease-sym to-right?)
+(define *ease-cells* #f)
+
+(define *knock-ent* #f)
+(define *knock-tw* #f)
+(define *knock-cd* 0)
+
+(define +knock-skip+
+  '(jump acceleration gravity velocity-x velocity-y))
+
+(define *ease-syms*
+  '(linear quad-in quad-out quad-in-out cubic-in cubic-out cubic-in-out
+    sine-in-out expo-in expo-out expo-in-out back-out))
+
+(define *label-font* #f)
+(define *title-font* #f)
+
+(define +tile-ids+ '#(24 73 122 171 220))
+
+(define (make-ease-cell ease-sym y tile-id)
+  (let* ((left 20)
+         (right (+ left 120))
+         (ent (list #:type 'tween-demo #:x left #:y y #:width 14 #:height 14
+                    #:vx 0 #:vy 0 #:gravity? #f #:solid? #f #:tile-id tile-id))
+         (tw (make-tween ent props: `((#:x . ,right)) duration: 2600 ease: ease-sym)))
+    (vector ent tw left right ease-sym #t)))
+
+(define (advance-ease-cell! cell dt)
+  (let ((ent (vector-ref cell 0))
+        (tw (vector-ref cell 1))
+        (left (vector-ref cell 2))
+        (right (vector-ref cell 3))
+        (ease (vector-ref cell 4))
+        (to-right? (vector-ref cell 5)))
+    (receive (tw2 ent2) (tween-step tw ent dt)
+      (vector-set! cell 0 ent2)
+      (cond ((tween-finished? tw2)
+             (let* ((next-to-right? (not to-right?))
+                    (target-x (if next-to-right? right left))
+                    (tw3 (make-tween ent2 props: `((#:x . ,target-x))
+                                     duration: 2600 ease: ease)))
+               (vector-set! cell 1 tw3)
+               (vector-set! cell 5 next-to-right?)))
+            (else (vector-set! cell 1 tw2))))))
+
+(define (update-knockback! dt tm)
+  (set! *knock-cd* (+ *knock-cd* dt))
+  (when (and *knock-ent* (not *knock-tw*) (>= *knock-cd* 3200))
+    (set! *knock-cd* 0)
+    (let ((x (entity-ref *knock-ent* #:x 0)))
+      (set! *knock-ent* (entity-set *knock-ent* #:skip-pipelines +knock-skip+))
+      (set! *knock-tw* (make-tween *knock-ent*
+                      props: `((#:x . ,(+ x 88)))
+                      duration: 650
+                      ease: 'back-out
+                      on-complete: (lambda (e)
+                                     (set! *knock-ent* (entity-set e #:skip-pipelines '())))))))
+  (when *knock-tw*
+    (receive (t2 e2) (tween-step *knock-tw* *knock-ent* dt)
+      (set! *knock-tw* (if (tween-finished? t2) #f t2))
+      (set! *knock-ent* e2)))
+  (when *knock-ent*
+    (set! *knock-ent*
+      (let* ((e *knock-ent*)
+             (e (apply-jump e #f))
+             (e (apply-acceleration e))
+             (e (apply-gravity e))
+             (e (apply-velocity-x e))
+             (e (resolve-tile-collisions-x e tm))
+             (e (apply-velocity-y e))
+             (e (resolve-tile-collisions-y e tm))
+             (e (detect-ground e tm)))
+        e))))
+
+(define (tweens-demo-render-labels! renderer)
+  (let ((white (sdl2:make-color 255 255 255 255)))
+    (draw-ui-text renderer *title-font*
+      "Tween demo — easing rows + knockback / skip-pipelines" white 12 6)
+    (draw-ui-text renderer *label-font*
+      "Each box loops on X; bottom crate tweens right with physics integration skipped, tiles still collide."
+      white 12 32)
+    (do ((i 0 (+ i 1))) ((>= i (vector-length *ease-cells*)))
+      (let* ((cell (vector-ref *ease-cells* i))
+             (ent (vector-ref cell 0))
+             (lab (symbol->string (vector-ref cell 4))))
+        (draw-ui-text renderer *label-font* lab white 158 (- (entity-ref ent #:y 0) 2))))))
+
+(define *game*
+  (make-game
+    title: "Demo: Tweens" width: 640 height: 480
+    preload: (lambda (_game)
+      (set! *title-font* (ttf:open-font "demo/assets/DejaVuSans.ttf" 22))
+      (set! *label-font* (ttf:open-font "demo/assets/DejaVuSans.ttf" 13)))
+    create: (lambda (game)
+      (let ((scene (game-load-scene! game "demo/assets/level-0.tmx")))
+        (set! *ease-cells*
+          (list->vector
+            (map (lambda (ease i)
+                   (make-ease-cell ease (+ 52 (* i 20))
+                     (vector-ref +tile-ids+ (modulo i (vector-length +tile-ids+)))))
+                 *ease-syms*
+                 (iota (length *ease-syms*)))))
+        (set! *knock-ent*
+          (list #:type 'knock-crate #:x 200 #:y 80 #:width 18 #:height 18
+                #:vx 0 #:vy 0 #:gravity? #t #:on-ground? #f #:solid? #f #:tile-id 220))
+        (set! *knock-tw* #f)
+        (set! *knock-cd* 2500)
+        (scene-entities-set! scene
+          (append (map (lambda (i) (vector-ref (vector-ref *ease-cells* i) 0))
+                       (iota (vector-length *ease-cells*)))
+                  (list *knock-ent*)))))
+    update: (lambda (game dt)
+      (let* ((scene (game-scene game)) (tm (scene-tilemap scene)))
+        (do ((i 0 (+ i 1))) ((>= i (vector-length *ease-cells*)))
+          (advance-ease-cell! (vector-ref *ease-cells* i) dt))
+        (update-knockback! dt tm)
+        (scene-entities-set! scene
+          (append (map (lambda (i) (vector-ref (vector-ref *ease-cells* i) 0))
+                       (iota (vector-length *ease-cells*)))
+                  (list *knock-ent*)))))
+    render: (lambda (game)
+      (tweens-demo-render-labels! (game-renderer game)))))
+
+(game-run! *game*)