OMFG I FIXED SKY SHARK

README.md

@@ -61,7 +61,7 @@ So far, the following mappers and associated games have been tested in this emul
   - Gyruss
   - Tiger Heli
 - 007
-  - Sky Shark (HUD is jumpy)
+  - Sky Shark
   - Marble Madness (text box glitches a little at start of level)
   - Wheel of Fortune
 

happiNESs/Address.swift

@@ -29,6 +29,7 @@ enum AddressBitMask: Address {
     case coarseY    = 0b0000_0011_1110_0000
     case coarseX    = 0b0000_0000_0001_1111
 
+    case bit14      = 0b0100_0000_0000_0000
     case highByte   = 0b0011_1111_0000_0000
     case lowByte    = 0b0000_0000_1111_1111
 

happiNESs/PPU+IO.swift

@@ -37,7 +37,15 @@ extension PPU {
 
     mutating public func updateAddress(byte: UInt8) {
         if !self.wRegister {
+            // ACHTUNG! Per the following excerpt in the NESDev wiki for PPUADDR, we
+            // need to _explicitly_ reset bit 14 here:
+            //
+            //     "However, bit 14 of the internal t register that holds the data written
+            //     to PPUADDR is forced to 0 when writing the PPUADDR high byte"
+            //
+            //     https://www.nesdev.org/wiki/PPU_registers#PPUADDR_-_VRAM_address_($2006_write)
             self.nextSharedAddress[.highByte] = byte
+            self.nextSharedAddress[.bit14] = 0
         } else {
             self.nextSharedAddress[.lowByte] = byte
             self.currentSharedAddress = self.nextSharedAddress

happiNESs/PPU+caching.swift

@@ -195,7 +195,7 @@ extension PPU {
     }
 
     private func getSpriteData(for oamIndex: Int) -> UInt32 {
-        let tileY = Int(self.oamRegister.data[oamIndex]) + 1
+        let tileY = Int(self.oamRegister.data[oamIndex])
         let attributeByte = self.oamRegister.data[oamIndex + 2]
 
         let flipVertical = ((attributeByte >> 7) & 1) == 1
@@ -285,7 +285,7 @@ extension PPU {
             // ACHTUNG! Note that the value in OAM is one less than the actual Y value!
             //
             //    https://www.nesdev.org/wiki/PPU_OAM#Byte_0
-            let tileY = Int(self.oamRegister.data[oamIndex]) + 1
+            let tileY = Int(self.oamRegister.data[oamIndex])
 
             let spritePixelY = self.scanline - tileY
             // The sprite height property takes into account whether or not all
@@ -328,7 +328,7 @@ extension PPU {
             // Reset coarse X
             self.currentSharedAddress[.coarseX] = 0b0_0000
             // Toggle horizontal nametable
-            self.currentSharedAddress[.nametable] ^= 0b01
+            self.currentSharedAddress[.nametableX] ^= 0b1
         } else {
             // Just increment coarse X
             self.currentSharedAddress[.coarseX] += 0b0_0001
@@ -344,7 +344,7 @@ extension PPU {
                 // Reset coarse Y
                 self.currentSharedAddress[.coarseY] = 0b0_0000
                 // Toggle vertical nametable
-                self.currentSharedAddress[.nametable] ^= 0b10
+                self.currentSharedAddress[.nametableY] ^= 0b1
             } else if self.currentSharedAddress[.coarseY] == 0b1_1111 {
                 // ACHTUNG! How would we ever get to this branch?
                 //

happiNESs/PPU+rendering.swift

@@ -20,13 +20,21 @@ extension PPU {
     }
 
     private func getCurrentBackgroundTileColor() -> NESColor? {
+        if self.maskRegister[.showBackground] == false {
+            return nil
+        }
+
         let tileData = self.currentTileData
         let pixelData = tileData >> ((7 - self.currentFineX) * 4)
         let colorIndex = Int(pixelData & 0x0F)
         return colorIndex.isMultiple(of: 4) ? nil : NESColor.systemPalette[Int(self.paletteTable[colorIndex])]
     }
 
     private func getCurrentSpriteColor() -> (color: NESColor, index: Int, backgroundPriority: Bool)? {
+        if self.maskRegister[.showSprites] == false {
+            return nil
+        }
+
         // Note that `currentSprites` is ordered from left to right by the OAM index,
         // with the first (zeroth) element being the so-called sprite zero. Furthermore,
         // the strategy here is to find the first sprite whose pixels intersect with the

happiNESs/PPU.swift

@@ -118,10 +118,13 @@ public struct PPU {
         self.cycles >= 1 && self.cycles <= Self.width
     }
     var isIncrementVerticalScrollCycle: Bool {
-        self.cycles == Self.width + 1
+        self.cycles == Self.width
     }
     var isCopyHorizontalScrollCycle: Bool {
-        self.cycles == Self.width + 2
+        self.cycles == Self.width + 1
+    }
+    var isCacheSpritesCycle: Bool {
+        self.cycles == Self.width + 1
     }
     var isCopyVerticalScrollCycle: Bool {
         self.cycles >= 280 && self.cycles <= 304
@@ -161,7 +164,7 @@ public struct PPU {
             self.cacheBackgroundTiles()
 
             // TODO: Revisit this because sprites should be cached for the _next_ line
-            if self.isVisibleLine && self.cycles == 0 {
+            if self.isVisibleLine && self.isCacheSpritesCycle {
                 self.cacheSprites()
             }
         }
@@ -239,7 +242,7 @@ public struct PPU {
             self.handleNmiState()
             self.handleRendering()
             self.handleCaching()
-            redrawScreen = redrawScreen || self.handleVerticalBlank()
+            redrawScreen = self.handleVerticalBlank() || redrawScreen
             self.handleFrameCounts()
         }
 

happiNESs/Register.swift

@@ -13,6 +13,7 @@ extension Register {
             (self & (1 << flag.bitIndex)) > 0
         }
         set {
+            self &= ~(1 << flag.bitIndex)
             self |= (newValue ? 1 : 0) << flag.bitIndex
         }
     }

happiNESsApp/Speaker.swift

@@ -42,7 +42,7 @@ struct Speaker {
         engine.attach(sourceNode)
         engine.connect(sourceNode, to: mainMixer, format: inputFormat)
         engine.connect(mainMixer, to: output, format: outputFormat)
-        mainMixer.outputVolume = 0.5
+        mainMixer.outputVolume = 1.0
 
         try engine.start()
     }