fix: improve types of heap allocated arrays

src/ppu.rs

@@ -8,8 +8,8 @@ pub struct Ppu {
     pub lcd_control: LCDControl,
     pub monochrome: Monochrome,
     pub pos: ScreenPosition,
-    pub vram: Box<[u8]>,
-    pub oam: Box<[u8]>,
+    pub vram: Box<[u8; 8192]>,
+    pub oam: Box<[u8; 160]>,
     frame_buf: [u8; GB_WIDTH * GB_HEIGHT * 4],
     pub stat: LCDStatus,
     cycles: Cycles,
@@ -81,8 +81,8 @@ impl Default for Ppu {
             monochrome: Default::default(),
             pos: Default::default(),
             stat: Default::default(),
-            vram: vec![0; 8192].into_boxed_slice(),
-            oam: vec![0; 160].into_boxed_slice(),
+            vram: Box::new([0u8; 8192]),
+            oam: Box::new([0u8; 160]),
             cycles: 0.into(),
             frame_buf: [0; GB_WIDTH * GB_HEIGHT * 4],
         }