diff --git a/helianthus/SConstruct b/helianthus/SConstruct
index e8e3231..d0e63b6 100644
--- a/helianthus/SConstruct
+++ b/helianthus/SConstruct
@@ -23,6 +23,7 @@ sources = [
 	'common.c',
 	'drawing.c',
 	'group.c',
+	'test.c',
 	'sprite.c',
 	'world.c',
 	'main.c' ]
diff --git a/helianthus/array.c b/helianthus/array.c
index 6e87b14..d6b56d2 100644
--- a/helianthus/array.c
+++ b/helianthus/array.c
@@ -84,9 +84,13 @@ HeliPair* heliStringmapFind(HeliArray *a, const char *k, int *gtOrEqIndex) {
 		return cmp ? NULL : &a->items[i0];
 	}
 	if (i1 > i0) cmp = strcmp((char*)a->items[i1].key, k);
-	if (cmp <= 0) {
+	if (cmp < 0) {
 		if (gtOrEqIndex) *gtOrEqIndex = a->count;
-		return cmp ? NULL : &a->items[i1];
+		return NULL;
+	}
+	if (cmp == 0) {
+		if (gtOrEqIndex) *gtOrEqIndex = i1;
+		return &a->items[i1];
 	}
 	
 	while(i0 + 1 < i1) {
diff --git a/helianthus/main.c b/helianthus/main.c
index b0c0a49..0749ec6 100644
--- a/helianthus/main.c
+++ b/helianthus/main.c
@@ -8,15 +8,12 @@ Sprite ball, brick1, brick2;
 void init() {
 	ball = createSpriteEx(200, 200, 64, 64);
 	spriteSetAnimation(ball, "data/sprites/breadball.png");
-	spriteSetDebug(ball, TRUE);
 	
 	brick1 = createSpriteEx(200-32, 200+64, 64, 64);
 	spriteSetAnimation(brick1, "data/sprites/bricks.png");
-	spriteSetDebug(brick1, TRUE);
 	
 	brick2 = createSpriteEx(200+32, 200+64, 64, 64);
 	spriteSetAnimation(brick2, "data/sprites/bricks.png");
-	spriteSetDebug(brick2, TRUE);
 }
 
 void draw() {
@@ -32,6 +29,8 @@ void draw() {
 	if (keyDown("up"))    spriteSetY(ball, y - speed*dt);
 	if (keyDown("down"))  spriteSetY(ball, y + speed*dt);
 	
+	spriteSetSpeedAndDirection(ball, speed, spriteGetRotation(ball));
+	
 	drawSprites();
 }
 
diff --git a/helianthus/private.h b/helianthus/private.h
index 9949c2d..bd90baf 100644
--- a/helianthus/private.h
+++ b/helianthus/private.h
@@ -104,3 +104,9 @@ void heliSpriteFinish();
 
 void heliDrawingPrepareFrame();
 void heliDrawingFinish();
+
+
+// test
+
+void heliDoTests();
+
diff --git a/helianthus/sprite.c b/helianthus/sprite.c
index 57fb407..a6aaf81 100644
--- a/helianthus/sprite.c
+++ b/helianthus/sprite.c
@@ -331,15 +331,16 @@ static void drawSprite(cairo_t *cr, Sprite s) {
 	}
 	
 	// tint
+	#warning "TODO: tint was not implemented yet"
 	cairo_save(cr);
 	cairo_set_source_rgba(cr, s->tintColor[0], s->tintColor[1], s->tintColor[2], s->tintColor[3]);
-	cairo_set_operator(cr, CAIRO_OPERATOR_MULTIPLY);
+	cairo_set_operator(cr, CAIRO_OPERATOR_OUT);
 	cairo_move_to(cr, -hw, -hh);
 	cairo_line_to(cr,  hw, -hh);
 	cairo_line_to(cr,  hw,  hh);
 	cairo_line_to(cr, -hw,  hh);
 	cairo_close_path(cr);
-	cairo_fill(cr);
+	//cairo_fill(cr);
 	cairo_restore(cr);
 	
 	cairo_pop_group_to_source(cr);
diff --git a/helianthus/test.c b/helianthus/test.c
new file mode 100644
index 0000000..713f2cd
--- /dev/null
+++ b/helianthus/test.c
@@ -0,0 +1,60 @@
+
+#include "private.h"
+
+//#define HELI_DO_TESTS
+
+#ifndef HELI_DO_TESTS
+void heliDoTests() { }
+#else
+
+
+static printStringset(HeliArray *a) {
+	for(int i = 0; i < a->count; ++i)
+		printf("  %s\n", (const char*)a->items[i].key);
+}
+
+static void testStringSet() {
+	printf("-- testStringSet\n");
+	
+	static char *strings[] = {
+		"hello",
+		"apple",
+		"orange",
+		"pineapple",
+		"potato",
+		"carrot",
+		"grape",
+		"cucumber"
+	};
+	
+	HeliArray a = {};
+	for(int i = 0; i < (int)(sizeof(strings)/sizeof(*strings)); ++i)
+		heliStringmapAdd(&a, strings[i], NULL, NULL);
+	
+	printf("  fill:\n");
+	printStringset(&a);
+	
+	printf("\n -remove %s:\n", "hello");
+	heliStringmapRemove(&a, "hello");
+	printStringset(&a);
+
+	printf("\n -remove %s:\n", "apple");
+	heliStringmapRemove(&a, "apple");
+	printStringset(&a);
+	
+	printf("\n -remove %s:\n", "potato");
+	heliStringmapRemove(&a, "potato");
+	printStringset(&a);
+	
+	heliArrayDestroy(&a);
+
+	printf("-- end\n");
+}
+
+void heliDoTests() {
+	printf("---- doTests\n");
+	testStringSet();
+	printf("---- end\n");
+}
+
+#endif
diff --git a/helianthus/world.c b/helianthus/world.c
index 6a79902..df20ecf 100644
--- a/helianthus/world.c
+++ b/helianthus/world.c
@@ -168,6 +168,8 @@ static gboolean draw(GtkWidget *widget G_GNUC_UNUSED, cairo_t *cr, gpointer data
 	guint64 newTime = g_get_monotonic_time();
 	heliCairo = cr;
 
+	if (frameCount == 0) heliDoTests();
+	
 	double dt = 1/frameRate;
 	guint64 timeStep = (guint64)round(dt*1e6);
 	while(currentTime < newTime) {
@@ -200,7 +202,6 @@ static gboolean handleEvent(GtkWidget *widget G_GNUC_UNUSED, GdkEvent *event, gp
 		heliLowercase(keyname);
 		heliStringmapAdd(&keysPressed, keyname, NULL, NULL);
 		heliStringmapAdd(&keysPressedInFrame, keyname, NULL, NULL);
-		//printf("key pressed: %s\n", keyname);
 		free(keyname);
 		return TRUE;
 	case GDK_KEY_RELEASE: