Add some randomness

1 files changed, 24 insertions, 0 deletions

diff --git a/game/random.asm b/game/random.asm
new file mode 100644
index 0000000..0cb74db
--- /dev/null
+++ b/game/random.asm
@@ -0,0 +1,24 @@
+;
+; Random number generator
+;
+; x[i + 1] = (5 * x[i] + 1) mod 256
+;
+; out: y random value
+rnd:
+    ld x, <seed
+    ld a, >seed
+
+    ld y, [a : x]
+    ld b, y
+
+    add y, y
+    add y, y
+    add y, b
+    add y, 7
+
+    ld [a : x], y
+
+    ret
+
+seed:
+    .db 0