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(import scheme
(chicken base)
(chicken random)
(only srfi-1 iota take)
(only srfi-197 chain)
(prefix sdl2 "sdl2:")
(prefix sdl2-ttf "ttf:")
(prefix sdl2-image "img:")
downstroke-engine
downstroke-world
downstroke-tilemap
downstroke-physics
downstroke-assets
downstroke-entity
downstroke-scene-loader
downstroke-tween
downstroke-prefabs)
;; ── Constants ────────────────────────────────────────────────────────────────
(define +game-width+ 600)
(define +game-height+ 400)
(define +demo-bot-cycle-ms+ 2600.0)
(define +demo-bot-half-cycle-ms+ (/ +demo-bot-cycle-ms+ 2.0))
(define +demo-bot-jump-interval-ms+ 720.0)
;; ── Mutable demo state ──────────────────────────────────────────────────────
(define *demo-t* 0.0)
(define *shelf-endpoints* #f)
(define *shelf-tween* #f)
(define *shelf-origin* #f)
;; ── Tween helpers ────────────────────────────────────────────────────────────
(define (other-endpoint x endpoints)
(let ((lo (car endpoints))
(hi (cdr endpoints)))
(if (< (abs (- x lo)) (abs (- x hi))) hi lo)))
(define (make-ping-pong-tween leader endpoints)
(make-tween leader
props: `((#:x . ,(other-endpoint (entity-ref leader #:x 0) endpoints)))
duration: 3500 ease: 'sine-in-out))
(define (scene-replace-group-origin! scene gid new-origin)
(scene-entities-set! scene
(map (lambda (e)
(if (and (entity-ref e #:group-origin? #f)
(eq? (entity-ref e #:group-id) gid))
new-origin
e))
(scene-entities scene))))
(define (advance-shelf-tween! scene dt)
(when (and *shelf-tween* *shelf-origin*)
(let ((gid (entity-ref *shelf-origin* #:group-id)))
(receive (tw2 e0) (tween-step *shelf-tween* *shelf-origin* dt)
(set! *shelf-tween* (if (tween-finished? tw2)
(make-ping-pong-tween e0 *shelf-endpoints*)
tw2))
(set! *shelf-origin* e0)
(scene-replace-group-origin! scene gid e0)))))
;; ── Tilemap builder ──────────────────────────────────────────────────────────
(define (make-sandbox-tilemap ts tw th gw gh)
(let* ((ncols (inexact->exact (ceiling (/ gw tw))))
(nrows (inexact->exact (ceiling (/ gh th))))
(empty-row (map (lambda (_) 0) (iota ncols)))
(floor-row (map (lambda (_) 20) (iota ncols)))
(map-data (append (map (lambda (_) empty-row) (iota (- nrows 1)))
(list floor-row))))
(make-tilemap
width: ncols height: nrows
tilewidth: tw tileheight: th
tileset-source: "" tileset: ts
layers: (list (make-layer name: "ground"
width: ncols height: nrows
map: map-data))
objects: '())))
;; ── Entity factories ─────────────────────────────────────────────────────────
(define (make-box x y tw th)
(list #:type 'box
#:x x #:y y #:width tw #:height th
#:vx 0 #:vy 0
#:gravity? #t #:on-ground? #f
#:solid? #t #:immovable? #f
#:tile-id 29))
(define (spawn-boxes tw th)
(map (lambda (i)
(make-box (+ 30 (* i 55))
(+ 10 (* (pseudo-random-integer 4) 20))
tw th))
(iota 8)))
(define (make-demo-bot x y tw th id)
(list #:type 'demo-bot
#:x x #:y y #:width tw #:height th
#:vx 0 #:vy 0
#:gravity? #t #:on-ground? #f
#:solid? #t #:immovable? #f
#:tile-id 1
#:demo-id id #:demo-since-jump 0))
;; ── Per-entity physics ──────────────────────────────────────────────────────
(define (run-physics e tm)
(chain e
(apply-gravity _)
(apply-velocity-x _)
(resolve-tile-collisions-x _ tm)
(apply-velocity-y _)
(resolve-tile-collisions-y _ tm)))
(define (update-demo-bot e dt tm)
(let* ((id (entity-ref e #:demo-id 0))
(phase (modulo (+ *demo-t* (* id 400.0)) +demo-bot-cycle-ms+))
(vx (if (< phase +demo-bot-half-cycle-ms+) 3.0 -3.0))
(e (entity-set e #:vx vx))
(ground? (entity-ref e #:on-ground? #f))
(since (+ (entity-ref e #:demo-since-jump 0) dt))
(jump? (and ground? (>= since +demo-bot-jump-interval-ms+)))
(since (if jump? 0 since)))
(chain (entity-set e #:demo-since-jump since)
(apply-jump _ jump?)
(apply-acceleration _)
(run-physics _ tm))))
(define (integrate-entity e dt tm)
(case (entity-type e)
((demo-bot) (update-demo-bot e dt tm))
((box) (run-physics e tm))
(else
(if (and (entity-ref e #:group-origin? #f)
(entity-ref e #:gravity? #f))
(run-physics e tm)
e))))
;; ── Scene builder ───────────────────────────────────────────────────────────
(define (init-shelf-tween! shelf-list tw)
(let* ((origin (car shelf-list))
(x-left (entity-ref origin #:x 0))
(x-right (+ x-left (* 6 tw))))
(set! *shelf-origin* origin)
(set! *shelf-endpoints* (cons x-left x-right))
(set! *shelf-tween* (make-ping-pong-tween origin *shelf-endpoints*))))
(define (make-sandbox-scene game)
(let* ((reg (load-prefabs "demo/assets/sandbox-groups.scm" (engine-mixins) '()))
(ts (game-load-tileset! game 'tileset "demo/assets/monochrome_transparent.tsx"))
(tw (tileset-tilewidth ts))
(th (tileset-tileheight ts))
(tex (create-texture-from-tileset (game-renderer game) ts))
(gw (game-width game))
(gh (game-height game))
(tm (make-sandbox-tilemap ts tw th gw gh))
(shelf-list (instantiate-group-prefab reg 'shelf-platform
(* 10 tw) (- gh (* 6 th))))
(raft-list (instantiate-group-prefab reg 'collision-raft
120 (- gh (* 14 th))))
(bots (list (make-demo-bot 80 80 tw th 0)
(make-demo-bot 220 60 tw th 1)
(make-demo-bot 380 100 tw th 2))))
(init-shelf-tween! shelf-list tw)
(make-scene
entities: (append shelf-list raft-list (spawn-boxes tw th) bots)
tilemap: tm
tileset: #f
camera: (make-camera x: 0 y: 0)
tileset-texture: tex
camera-target: #f
background: '(32 34 40))))
;; ── Game ─────────────────────────────────────────────────────────────────────
(define *game*
(make-game
title: "Demo: Physics Sandbox"
width: +game-width+ height: +game-height+
create: (lambda (game)
(game-scene-set! game (make-sandbox-scene game)))
update: (lambda (game dt)
(set! *demo-t* (+ *demo-t* dt))
(let* ((scene (game-scene game))
(tm (scene-tilemap scene)))
(advance-shelf-tween! scene dt)
(scene-update-entities scene (lambda (e) (integrate-entity e dt tm)))
(scene-sync-groups! scene)
(scene-resolve-collisions scene)
(scene-update-entities scene
(lambda (e)
(if (entity-ref e #:gravity? #f)
(detect-on-solid e tm (scene-entities scene))
e)))))))
(game-run! *game*)
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