Add chaining.

3 files changed, 59 insertions, 10 deletions

diff --git a/assets/images/chain.png b/assets/images/chain.png
new file mode 100644
index 0000000..dc59d12
--- /dev/null
+++ b/assets/images/chain.png
diff --git a/assets/images/chain.xcf b/assets/images/chain.xcf
new file mode 100644
index 0000000..40fecd9
--- /dev/null
+++ b/assets/images/chain.xcf
diff --git a/game.scm b/game.scm
index 2571048..ad90be6 100644
--- a/game.scm
+++ b/game.scm
@@ -270,7 +270,7 @@
 
 (define max-chain-multiplier 10)
 
-(define (add-to-score stats enemy)
+(define (add-to-score enemy stats)
   ;; TODO: Award different points for different types of enemies.
   (make-stats #:inherit stats
               #:score (+ (stats-score stats)
@@ -280,6 +280,27 @@
                             (min (stats-chain stats)
                                  max-chain-multiplier)))))
 
+(define (add-to-chain enemy stats)
+  (let* ((enemy-polarity (enemy-polarity enemy))
+         (chain-polarity (stats-chain-type stats))
+         (progress (stats-chain-progress stats)))
+    (cond
+     ((or (zero? progress) (= progress 3))
+      (make-stats #:inherit stats
+                  #:chain-type enemy-polarity
+                  #:chain-progress 1))
+     ((not (eq? enemy-polarity chain-polarity))
+      (make-stats #:inherit stats
+                  #:chain-type #f
+                  #:chain-progress 0))
+     ((= progress 1)
+      (make-stats #:inherit stats
+                  #:chain-progress 2))
+     ((= progress 2)
+      (make-stats #:inherit stats
+                  #:chain-progress 3
+                  #:chain (1+ (stats-chain stats)))))))
+
 
 ;;;
 ;;; Collision detection
@@ -324,24 +345,26 @@
          (values enemy (reverse prev-bullets) stats explosions))
         ((bullet . rest)
          (if (enemy/bullet-collision? (actor-ref enemy) (actor-ref bullet))
-             (let ((new-enemy (call-with-actor enemy
+             (let* ((new-enemy (call-with-actor enemy
                                 (lambda (enemy)
                                   (damage-enemy enemy
                                                 (actor-ref bullet)
-                                                time)))))
+                                                time))))
+                    (new-enemy* (actor-ref new-enemy)))
                (values new-enemy
                        ;; Remove bullet.
                        (append (reverse prev-bullets) rest)
-                       (if (enemy-alive? (actor-ref new-enemy))
+                       (if (enemy-alive? new-enemy*)
                            stats
-                           ;; Enemy killed, add to player score.
-                           (add-to-score stats (actor-ref new-enemy)))
-                       (if (enemy-alive? (actor-ref new-enemy))
+                           ;; Enemy killed, add to player score and
+                           (add-to-chain new-enemy*
+                                         (add-to-score new-enemy* stats)))
+                       (if (enemy-alive? new-enemy*)
                            explosions
                            ;; Add new explosion.
                            (cons (make-explosion #:type 'regular
                                                  #:position (enemy-position
-                                                             (actor-ref enemy))
+                                                             new-enemy*)
                                                  #:time time)
                                  explosions))))
              (loop rest (cons bullet prev-bullets) stats))))))
@@ -673,6 +696,30 @@ each time KEY is pressed."
 (define-signal explosion-tileset
   (load-tileset/live "assets/images/explosion.png" 16 16))
 
+(define-signal chain-tileset
+  (load-tileset/live "assets/images/chain.png" 24 16))
+
+(define make-chain-sprite
+  (memoize
+   (lambda (tileset stats)
+     (make-sprite (tileset-ref tileset
+                               (- (match (stats-chain-type stats)
+                                    ('light 2)
+                                    ('dark  5))
+                                  (1- (stats-chain-progress stats))))
+                  #:anchor 'top-left))))
+
+(define-signal chain-sprite
+  (signal-map-maybe (lambda (world tileset)
+                      (let ((stats (world-stats world)))
+                        (if (zero? (stats-chain-progress stats))
+                            render-nothing
+                            (move (vector2 0 (- (vy resolution) 5))
+                                  (render-sprite
+                                   (make-chain-sprite tileset stats))))))
+                    world
+                    chain-tileset))
+
 (define-signal player-sprite
   (signal-map-maybe (lambda (world tileset)
                       (make-sprite
@@ -798,6 +845,7 @@ each time KEY is pressed."
                (framebuffer framebuffer)
                (framebuffer-sprite framebuffer-sprite)
                (player-sprite player-sprite)
+               (chain-sprite chain-sprite)
                (bullet-tileset bullet-tileset)
                (enemy-tileset enemy-tileset)
                (explosion-tileset explosion-tileset)
@@ -805,7 +853,7 @@ each time KEY is pressed."
                (world world)
                (time timer))
     (if (and framebuffer framebuffer-sprite batch bullet-tileset
-             enemy-tileset player-sprite explosion-tileset)
+             enemy-tileset player-sprite explosion-tileset chain-sprite)
         (let ((player (actor-ref (world-player world))))
           (render-begin
            (with-framebuffer framebuffer
@@ -834,7 +882,8 @@ each time KEY is pressed."
                        render-nothing)
                    score-text
                    lives-text
-                   chain-text)))))
+                   chain-text))
+                chain-sprite)))
            (with-camera scaled-camera
              (scale resolution-scale (render-sprite framebuffer-sprite)))))
         render-nothing)))