Make randomness a bit more random

Signed-off-by: Miquel Sabaté Solà <mssola@mssola.com>

3 files changed, 23 insertions, 20 deletions

diff --git a/bin/rand.rb b/bin/rand.rb
index a3e7e41..345cb4d 100644
--- a/bin/rand.rb
+++ b/bin/rand.rb
@@ -18,10 +18,13 @@ GROUND_Y_COORD = 0xC8 - 64
 # The available values for the Y axis for enemies are above ground, below the
 # sky, and avoiding the left-most and right-most platforms.
 available = (UPPER_MARGIN_Y_COORD..GROUND_Y_COORD).to_a - (0x58..0x69).to_a - (0x40..0x50).to_a
+available = available.shuffle
 
 # With this produce the array containing a randomized sample from the
 # 'available' values.
-random_byte_array = Array.new(256) { format('$%02X', available.sample) }
+random_byte_array = (0...256).map do |i|
+  format('$%02X', available[i % available.length])
+end
 
 # And now print it in the assembler format.
 random_byte_array.each_slice(16) do |row|
diff --git a/src/interrupts.s b/src/interrupts.s
index b5120b4..522ee9e 100644
--- a/src/interrupts.s
+++ b/src/interrupts.s
@@ -24,6 +24,9 @@
     lda #$02
     sta OAM::m_dma
 
+    ;; Increase the random seed.
+    inc Prng::zp_rand
+
     ;; Are we paused? If so skip timers, PAL handler and the likes.
     lda #%00001000
     and Globals::zp_flags
@@ -61,9 +64,6 @@
     and #%00000001
     bne @ppu_registers
 
-    ;; Increase the random seed.
-    inc Prng::zp_rand
-
     ;; Decrease title timer.
     lda Title::zp_title_timer
     beq @ppu_registers
diff --git a/src/prng.s b/src/prng.s
index 1d2a132..c5ec474 100644
--- a/src/prng.s
+++ b/src/prng.s
@@ -28,19 +28,19 @@
 ;;
 ;; NOTE: generated via bin/rand.rb; read more on this there.
 valid_y_rand_table:
-    .byte $73, $54, $7E, $3F, $76, $77, $55, $72, $83, $6A, $81, $53, $52, $74, $80, $3A
-    .byte $86, $3C, $87, $74, $3D, $88, $7A, $82, $54, $72, $7B, $77, $77, $75, $88, $52
-    .byte $86, $6D, $80, $54, $79, $7A, $85, $7E, $82, $88, $7E, $7B, $74, $84, $71, $70
-    .byte $3F, $3A, $82, $70, $75, $3D, $74, $7F, $88, $86, $83, $75, $86, $70, $55, $7A
-    .byte $73, $6E, $88, $85, $6F, $7C, $3D, $3E, $55, $3B, $6C, $6D, $54, $76, $3E, $3B
-    .byte $6F, $51, $7D, $73, $83, $52, $82, $7F, $72, $3A, $55, $78, $85, $3B, $86, $6A
-    .byte $70, $82, $6A, $77, $3C, $76, $7C, $85, $51, $6A, $71, $6A, $78, $86, $3E, $3F
-    .byte $84, $7F, $3C, $53, $73, $6C, $7E, $3A, $86, $84, $7E, $75, $53, $3B, $78, $3B
-    .byte $56, $7A, $7A, $77, $85, $6E, $76, $86, $52, $85, $3B, $3D, $87, $81, $7B, $83
-    .byte $86, $3E, $7F, $3E, $6A, $57, $85, $73, $88, $6A, $7B, $6E, $81, $77, $3B, $3F
-    .byte $84, $3E, $55, $83, $88, $81, $55, $76, $7A, $57, $76, $7B, $6F, $7C, $76, $3E
-    .byte $55, $82, $75, $75, $3F, $3E, $7E, $6C, $3F, $81, $6C, $6C, $71, $3D, $3B, $3E
-    .byte $87, $7C, $85, $3E, $74, $80, $83, $3E, $80, $3B, $71, $51, $51, $6E, $53, $7B
-    .byte $3D, $3D, $56, $79, $3B, $54, $7E, $6D, $3A, $81, $3E, $85, $88, $6C, $57, $85
-    .byte $52, $87, $7A, $86, $82, $7D, $87, $73, $7A, $83, $70, $70, $88, $52, $80, $86
-    .byte $80, $7B, $55, $53, $6A, $81, $6B, $3F, $86, $3E, $7F, $84, $55, $53, $6B, $86
+    .byte $84, $76, $85, $80, $55, $7E, $7C, $73, $7F, $52, $79, $81, $53, $75, $3D, $51
+    .byte $54, $6C, $88, $3C, $87, $6E, $57, $82, $77, $3E, $6B, $86, $6A, $3A, $3F, $83
+    .byte $78, $7A, $72, $70, $7D, $6F, $6D, $71, $7B, $74, $3B, $56, $84, $76, $85, $80
+    .byte $55, $7E, $7C, $73, $7F, $52, $79, $81, $53, $75, $3D, $51, $54, $6C, $88, $3C
+    .byte $87, $6E, $57, $82, $77, $3E, $6B, $86, $6A, $3A, $3F, $83, $78, $7A, $72, $70
+    .byte $7D, $6F, $6D, $71, $7B, $74, $3B, $56, $84, $76, $85, $80, $55, $7E, $7C, $73
+    .byte $7F, $52, $79, $81, $53, $75, $3D, $51, $54, $6C, $88, $3C, $87, $6E, $57, $82
+    .byte $77, $3E, $6B, $86, $6A, $3A, $3F, $83, $78, $7A, $72, $70, $7D, $6F, $6D, $71
+    .byte $7B, $74, $3B, $56, $84, $76, $85, $80, $55, $7E, $7C, $73, $7F, $52, $79, $81
+    .byte $53, $75, $3D, $51, $54, $6C, $88, $3C, $87, $6E, $57, $82, $77, $3E, $6B, $86
+    .byte $6A, $3A, $3F, $83, $78, $7A, $72, $70, $7D, $6F, $6D, $71, $7B, $74, $3B, $56
+    .byte $84, $76, $85, $80, $55, $7E, $7C, $73, $7F, $52, $79, $81, $53, $75, $3D, $51
+    .byte $54, $6C, $88, $3C, $87, $6E, $57, $82, $77, $3E, $6B, $86, $6A, $3A, $3F, $83
+    .byte $78, $7A, $72, $70, $7D, $6F, $6D, $71, $7B, $74, $3B, $56, $84, $76, $85, $80
+    .byte $55, $7E, $7C, $73, $7F, $52, $79, $81, $53, $75, $3D, $51, $54, $6C, $88, $3C
+    .byte $87, $6E, $57, $82, $77, $3E, $6B, $86, $6A, $3A, $3F, $83, $78, $7A, $72, $70