diff --git a/Cargo.toml b/Cargo.toml
index 6e0ae5a..4de83a2 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,6 +14,9 @@ publish = false
 [dependencies]
 gba-proc-macro = "0.2.1"
 
+[profile.dev]
+panic = "abort"
+
 [profile.release]
 lto = true
 panic = "abort"
diff --git a/examples/key_demo.rs b/examples/key_demo.rs
index d63e68d..efe3d61 100644
--- a/examples/key_demo.rs
+++ b/examples/key_demo.rs
@@ -34,6 +34,7 @@ fn main(_argc: isize, _argv: *const *const u8) -> isize {
       let key = ((this_frame_key_raw >> i) & 1) > 0;
       mode3_draw_pixel(15 - i, 0, if key { green } else { red });
       mode3_draw_pixel(15 - i, 1, if key { green } else { red });
+      mode3_draw_pixel(50 - i, 10 / i, if key { green } else { red });
     }
 
     wait_until_vdraw();
diff --git a/src/intrinsics.rs b/src/intrinsics.rs
new file mode 100644
index 0000000..dc92f3e
--- /dev/null
+++ b/src/intrinsics.rs
@@ -0,0 +1,71 @@
+//! Intrinsics that LLVM looks for when compiling.
+
+/// Signed division
+#[no_mangle]
+#[inline]
+pub extern "aapcs" fn __aeabi_idiv(n: i32, d: i32) -> i32 {
+  assert!(d != 0);
+  let div_out: i32;
+  let _mod_out: i32;
+  unsafe {
+    asm!(/* assembly template */ "swi 0x06"
+        :/* output operands */ "={r0}"(div_out), "={r1}"(_mod_out)
+        :/* input operands */ "{r0}"(n), "{r1}"(d)
+        :/* clobbers */ "r3"
+        :/* options */
+    );
+  }
+  div_out
+}
+
+/// Signed division alias for glibc reasons
+#[no_mangle]
+#[inline]
+pub extern "aapcs" fn __divsi3(n: i32, d: i32) -> i32 {
+  // Note the different naming scheme.
+  __aeabi_idiv(n, d)
+}
+
+/// Unsigned division gets cast into signed values, divided, and cast back
+#[no_mangle]
+#[inline]
+pub extern "aapcs" fn __aeabi_uidiv(n: u32, d: u32) -> u32 {
+  __aeabi_idiv(n as i32, d as i32) as u32
+}
+
+/// Unsigned division alias for glibc reasons
+#[no_mangle]
+#[inline]
+pub extern "aapcs" fn __udivsi3(n: u32, d: u32) -> u32 {
+  // Note the different naming scheme.
+  __aeabi_uidiv(n, d)
+}
+
+/// Count leading zeroes, required in debug mode for unknown reasons
+#[no_mangle]
+#[inline]
+pub extern "aapcs" fn __clzsi2(x: i32) -> i32 {
+  let mut y = -(x >> 16); // If left half of x is 0,
+  let mut m = (y >> 16) & 16; // set n = 16. If left half
+  let mut n = 16 - m; // is nonzero, set n = 0 and
+  let mut x = x >> m; // shift x right 16.
+                      // Now x is of the form 0000xxxx.
+  y = x - 0x100; // If positions 8-15 are 0,
+  m = (y >> 16) & 8; // add 8 to n and shift x left 8.
+  n = n + m;
+  x = x << m;
+
+  y = x - 0x1000; // If positions 12-15 are 0,
+  m = (y >> 16) & 4; // add 4 to n and shift x left 4.
+  n = n + m;
+  x = x << m;
+
+  y = x - 0x4000; // If positions 14-15 are 0,
+  m = (y >> 16) & 2; // add 2 to n and shift x left 2.
+  n = n + m;
+  x = x << m;
+
+  y = x >> 14; // Set y = 0, 1, 2, or 3.
+  m = y & !(y >> 1); // Set m = 0, 1, 2, or 2 resp.
+  n + 2 - m
+}
diff --git a/src/io_registers.rs b/src/io_registers.rs
index 120aae7..3682f64 100644
--- a/src/io_registers.rs
+++ b/src/io_registers.rs
@@ -116,6 +116,18 @@ pub fn vcount() -> u16 {
   unsafe { VCOUNT.read() }
 }
 
+/// Performs a busy loop until VBlank starts.
+pub fn wait_until_vblank() {
+  // TODO: make this the better version with BIOS and interrupts and such.
+  while vcount() < SCREEN_HEIGHT as u16 {}
+}
+
+/// Performs a busy loop until VDraw starts.
+pub fn wait_until_vdraw() {
+  // TODO: make this the better version with BIOS and interrupts and such.
+  while vcount() >= SCREEN_HEIGHT as u16 {}
+}
+
 /// BG0 Control
 pub const BG0CNT: VolatilePtr<u16> = VolatilePtr(0x4000008 as *mut u16);
 
diff --git a/src/lib.rs b/src/lib.rs
index 7c74928..ab35f5e 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -1,4 +1,5 @@
 #![cfg_attr(not(test), no_std)]
+#![feature(asm)]
 #![warn(missing_docs)]
 
 //! This crate helps you write GBA ROMs.
@@ -26,11 +27,41 @@ pub mod core_extras;
 pub(crate) use crate::core_extras::*;
 
 pub mod io_registers;
-pub(crate) use crate::io_registers::*;
 
 pub mod video_ram;
+pub(crate) use crate::video_ram::*;
+
+pub mod intrinsics;
 
 /// Combines the Red, Blue, and Green provided into a single color value.
 pub const fn rgb16(red: u16, green: u16, blue: u16) -> u16 {
   blue << 10 | green << 5 | red
 }
+
+/// BIOS Call: Div (GBA SWI 0x06).
+///
+/// Gives the DIV and MOD output of `numerator / denominator`.
+///
+/// # Panics
+///
+/// If `denominator` is 0.
+#[inline]
+pub fn div_mod(numerator: i32, denominator: i32) -> (i32, i32) {
+  // The BIOS includes several System Call Functions which can be accessed by
+  // SWI instructions. Incoming parameters are usually passed through registers
+  // R0,R1,R2,R3. Outgoing registers R0,R1,R3 are typically containing either
+  // garbage, or return value(s). All other registers (R2,R4-R14) are kept
+  // unchanged. --GBATEK
+  assert!(denominator != 0);
+  let div_out: i32;
+  let mod_out: i32;
+  unsafe {
+    asm!(/* assembly template */ "swi 0x06"
+        :/* output operands */ "={r0}"(div_out), "={r1}"(mod_out)
+        :/* input operands */ "{r0}"(numerator), "{r1}"(denominator)
+        :/* clobbers */ "r3"
+        :/* options */
+    );
+  }
+  (div_out, mod_out)
+}
diff --git a/src/video_ram.rs b/src/video_ram.rs
index de9ac04..c4d1601 100644
--- a/src/video_ram.rs
+++ b/src/video_ram.rs
@@ -28,18 +28,6 @@ pub const SCREEN_HEIGHT: isize = 160;
 /// value as just being a `usize`.
 pub const VRAM_BASE_ADDRESS: usize = 0x0600_0000;
 
-/// Performs a busy loop until VBlank starts.
-pub fn wait_until_vblank() {
-  // TODO: make this the better version with BIOS and interrupts and such.
-  while vcount() < SCREEN_HEIGHT as u16 {}
-}
-
-/// Performs a busy loop until VDraw starts.
-pub fn wait_until_vdraw() {
-  // TODO: make this the better version with BIOS and interrupts and such.
-  while vcount() >= SCREEN_HEIGHT as u16 {}
-}
-
 /// Draws a pixel to the screen while in Display Mode 3, with bounds checks.
 ///
 /// # Panics