feat(ppu): improve timings + implement BG mode 3 bitmap

src/emu.zig

@@ -2,7 +2,7 @@ const Bus = @import("Bus.zig");
 const Scheduler = @import("scheduler.zig").Scheduler;
 const Arm7tdmi = @import("cpu.zig").Arm7tdmi;
 
-const cycles_per_frame: u64 = 160 * (308 * 4);
+const cycles_per_frame: u64 = 100; // TODO: How many cycles actually?
 
 pub fn runFrame(sched: *Scheduler, cpu: *Arm7tdmi, bus: *Bus) void {
     var cycles: u64 = 0;

src/scheduler.zig

@@ -53,7 +53,7 @@ pub const Scheduler = struct {
                     } else {
                         // Transitioning to a Vblank
                         bus.io.dispstat.vblank.set();
-                        self.push(.{ .kind = .VBlank, .tick = self.tick + (308 * 4) });
+                        self.push(.{ .kind = .VBlank, .tick = self.tick + 68 * (308 * 4) });
                     }
                 },
                 .Draw => {
@@ -72,7 +72,7 @@ pub const Scheduler = struct {
 
                     if (new_scanline < 228) {
                         // Transition to another Vblank
-                        self.push(.{ .kind = .VBlank, .tick = self.tick + (308 * 4) });
+                        self.push(.{ .kind = .VBlank, .tick = self.tick + 68 * (308 * 4) });
                     } else {
                         // Transition to another Draw
                         bus.io.vcount.scanline.write(0); // Reset Scanline