Start with a skeleton for the project

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

1 files changed, 34 insertions, 0 deletions

diff --git a/include/globals.s b/include/globals.s
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+;; Global variables used throughout the code base.
+.scope Globals
+    ;;;
+    ;; Argument values as defined in https://github.com/mssola/style.nes. Note
+    ;; that these variables can also be used as temporary variables.
+    zp_arg0 = $00
+    zp_arg1 = $01
+    zp_arg2 = $02
+    zp_arg3 = $03
+    zp_arg4 = $04
+
+    ;;;
+    ;; Random values that can be used inside of functions for temporary values
+    ;; so `zp_argX` variables are not overwritten as often.
+    zp_tmp0 = $05
+    zp_tmp1 = $06
+    zp_tmp2 = $07
+    zp_tmp3 = $08
+
+    ;;;
+    ;; Reserve a byte of memory for preserving indices on memory. This is needed
+    ;; whenever the `x` and `y` registers might not be reliable because of
+    ;; underlying `jsr` calls that might tamper with their values. Sometimes
+    ;; saving the value in memory is enough instead of playing with the stack.
+    zp_idx = $09
+
+    ;; Flags that manage the state of the game.
+    ;;
+    ;; | Bit | Short name | Meaning when set                                            |
+    ;; |-----+------------+-------------------------------------------------------------|
+    ;; |   7 | render     | Game logic is over, block main code until NMI code is over. |
+    ;; | 6-0 | -          | Unused                                                      |
+    zp_flags = $20
+.endscope