Fix visual glitch in demo game

This was only happening on Mega Drive, not
the emalators... anyway, fixed now

src/game.rb

@@ -385,7 +385,7 @@ def scroll_wait
       break if (pad_state & 0x80 & ~prev) != 0 # start
       break if (pad_state & 0x40 & ~prev) != 0 # a
       prev = pad_state
-      wait_vblank(false)
+      wait_vblank(@show_timer)
     end
   end
 
@@ -396,6 +396,8 @@ def demo_game
     v_vel = 0
     prev = MegaMrbc.read_joypad
     spike_pos = 0
+    MegaMrbc.show_spikes(spike_pos)
+    MegaMrbc.show_runner(v_pos)
     while true do
       MegaMrbc.scroll_game
       spike_pos -= 6
@@ -411,8 +413,8 @@ def demo_game
       v_pos += v_vel
       v_pos = v_vel = 0 if v_pos >= 0
       prev = pad_state
-      MegaMrbc.show_spikes(spike_pos)
-      MegaMrbc.show_runner(v_pos)
+      MegaMrbc.set_spike_pos(spike_pos)
+      MegaMrbc.set_runner_pos(v_pos)
       if collided?(v_pos, spike_pos)
         MegaMrbc.sleep_raw(150)
         game_over
@@ -430,7 +432,7 @@ def game_over
     MegaMrbc.play_death_se
     while i < 30 do
       v_pos += 2
-      MegaMrbc.show_runner(v_pos)
+      MegaMrbc.set_runner_pos(v_pos)
       wait_vblank(false)
       i += 1
     end
@@ -444,8 +446,10 @@ def title_screen
     state = 0
     count = 0
     prev = MegaMrbc.read_joypad
+    MegaMrbc.render_start_bg
     [0, 1].each do |dash|
-      MegaMrbc.render_start(dash)
+      wait_vblank(false)
+      MegaMrbc.render_start_logo(dash)
       while true do
         MegaMrbc.scroll_title
         if count / 30 >= 1 # switch every 0.5s

src/main.c

@@ -327,7 +327,7 @@ Sprite* elephant0_obj;
 Sprite* elephant1_obj;
 Sprite* spikes_obj;
 
-static void render_sky_bg() {
+static void c_megamrbc_render_start_bg(mrb_vm *vm, mrb_value *v, int argc) {
   PAL_setPaletteDMA(PAL0, sky_bg.palette->data);
   VDP_drawImageEx(
     BG_B, &sky_bg,
@@ -336,15 +336,10 @@ static void render_sky_bg() {
   );
 }
 
-static void c_megamrbc_render_start_screen(mrb_vm *vm, mrb_value *v, int argc) {
+static void c_megamrbc_render_start_logo(mrb_vm *vm, mrb_value *v, int argc) {
   bool render_dash = mrbc_integer(v[1]);
   Image logo_image = main_logo;
 
-  // sprintf(buf, "colour_id: %d, colour_val: %d", colour_id, colour_val);
-  char str[40];
-  sprintf(str, "value: %d\n", render_dash);
-  KLog(str);
-  render_sky_bg();
   // use elephant palette which includes main logo palette
   VDP_setPalette(PAL1, elephant0.palette->data);
   if(render_dash) {
@@ -394,6 +389,13 @@ static void c_megamrbc_show_runner(mrb_vm *vm, mrb_value *v, int argc) {
   SPR_setVisibility(ninja32black_obj, VISIBLE);
 }
 
+// This has been moved out because calling show_spikes and show_runner every frame causes flickering on the actual unit, but not emulator
+// TODO: remove position from show_spikes / show_runner
+static void c_megamrbc_set_runner_pos(mrb_vm *vm, mrb_value *v, int argc) {
+  uint16_t v_pos = mrbc_integer(v[1]);
+  SPR_setPosition(ninja32black_obj, 130, 180 + v_pos);
+}
+
 static void c_megamrbc_show_spikes(mrb_vm *vm, mrb_value *v, int argc) {
   uint16_t spike_location = mrbc_integer(v[1]);
   // ninjas' shared pallette
@@ -402,6 +404,13 @@ static void c_megamrbc_show_spikes(mrb_vm *vm, mrb_value *v, int argc) {
   SPR_setVisibility(spikes_obj, VISIBLE);
 }
 
+// This has been moved out because calling show_spikes and show_runner every frame causes flickering on the actual unit, but not emulator
+// TODO: remove position from show_spikes / show_runner
+static void c_megamrbc_set_spike_pos(mrb_vm *vm, mrb_value *v, int argc) {
+  uint16_t spike_location = mrbc_integer(v[1]);
+  SPR_setPosition(spikes_obj, 320 + spike_location, 200);
+}
+
 static void c_megamrbc_hide_spikes(mrb_vm *vm, mrb_value *v, int argc) {
   SPR_setVisibility(spikes_obj, HIDDEN);
 }
@@ -826,11 +835,14 @@ void make_class(mrb_vm *vm)
   mrbc_define_method(vm, cls, "clear_screen", c_megamrbc_clear_screen);
   // mrbc_define_method(vm, cls, "is_word?", c_megamrbc_is_word);
   mrbc_define_method(vm, cls, "call_rand", c_megamrbc_call_rand);
-  mrbc_define_method(vm, cls, "render_start", c_megamrbc_render_start_screen);
+  mrbc_define_method(vm, cls, "render_start_bg", c_megamrbc_render_start_bg);
+  mrbc_define_method(vm, cls, "render_start_logo", c_megamrbc_render_start_logo);
   mrbc_define_method(vm, cls, "show_game_bg", c_megamrbc_show_game_bg);
   mrbc_define_method(vm, cls, "show_runner", c_megamrbc_show_runner);
+  mrbc_define_method(vm, cls, "set_runner_pos", c_megamrbc_set_runner_pos);
   mrbc_define_method(vm, cls, "hide_runner", c_megamrbc_hide_runner);
   mrbc_define_method(vm, cls, "show_spikes", c_megamrbc_show_spikes);
+  mrbc_define_method(vm, cls, "set_spike_pos", c_megamrbc_set_spike_pos);
   mrbc_define_method(vm, cls, "hide_spikes", c_megamrbc_hide_spikes);
   // Maybe not needed???
   mrbc_define_method(vm, cls, "read_content_line", c_megamrbc_read_content_line);