STEP01：rpg1.cを機能別に分割する設計とプロジェクト構成（main.cと各モジュール）

#ifndef COMMON_H
#define COMMON_H
/* ... */
#endif

/* main.c */
#include "common.h"
#include "platform.h"
#include "input.h"
#include "ui.h"
#include "map.h"
#include "services.h"
#include "items.h"
#include "characters.h"
#include "enemies.h"
#include "battle.h"

int main(void) {
    srand((unsigned)time(NULL));

    GameState gs;
    memset(&gs, 0, sizeof(gs));

    show_title();

    load_map_template(gs.map);
    gs.px = 1; gs.py = 1;
    gs.game_clear = 0;
    init_characters(gs.party);

    gs.inv[ITEM_POTION] = 2;
    gs.inv[ITEM_ETHER] = 1;

    while (1) {
        clear_screen();
        draw_map(&gs);

        printf("\nコマンド: 4/6/8/2=移動  s=セーブ  l=ロード  q=終了\n");
        printf("入力: ");

        char buf[64];
        read_line(buf, sizeof(buf));
        if (buf[0] == '\0') continue;

        if (buf[0] == 'q') {
            printf("終了します。\n");
            break;
        }

        if (buf[0] == 's') {
            if (save_game(&gs)) {
                sfx_beep(0);
                printf(GREEN "セーブしました。（%s）\n" RESET, SAVE_FILE);
            }
            else {
                sfx_beep(4);
                printf(RED "セーブに失敗しました。\n" RESET);
            }
            printf("Enterで続行...");
            read_line(buf, sizeof(buf));
            continue;
        }

        if (buf[0] == 'l') {
            GameState tmp;
            if (load_game(&tmp)) {
                gs = tmp;
                sfx_beep(0);
                printf(GREEN "ロードしました。（%s）\n" RESET, SAVE_FILE);
            }
            else {
                sfx_beep(4);
                printf(RED "ロードに失敗しました。（セーブデータがない可能性）\n" RESET);
            }
            printf("Enterで続行...");
            read_line(buf, sizeof(buf));
            continue;
        }

        int key = atoi(buf);
        int nx = gs.px, ny = gs.py;

        if (key == 4) ny--;
        else if (key == 6) ny++;
        else if (key == 8) nx--;
        else if (key == 2) nx++;
        else continue;

        if (nx < 0 || nx >= MAP_H || ny < 0 || ny >= MAP_W) continue;

        if (gs.map[nx][ny] != '#') {
            gs.px = nx; gs.py = ny;
        }

        char cell = gs.map[gs.px][gs.py];

        if (cell == 'T') {
            clear_screen();
            open_treasure_fixed(&gs, gs.px, gs.py);
            gs.map[gs.px][gs.py] = ' ';
            printf("Enterで続行...");
            read_line(buf, sizeof(buf));
        }
        else if (cell == 'I') {
            clear_screen();
            inn_rest(&gs);
            printf("Enterで続行...");
            read_line(buf, sizeof(buf));
        }
        else if (cell == 'C') {
            clear_screen();
            church_revive(&gs);
            printf("Enterで続行...");
            read_line(buf, sizeof(buf));
        }
        else if (cell == 'E') {
            Enemy e = make_random_enemy();

            int win = battle(&gs, e);
            if (win) {
                gs.map[gs.px][gs.py] = ' ';
                respawn_enemy(&gs);
            }
            else {
                clear_screen();
                printf(RED "ゲームオーバー…\n" RESET);
                printf("Enterでタイトルへ...");
                read_line(buf, sizeof(buf));

                show_title();
                load_map_template(gs.map);
                gs.px = 1; gs.py = 1;
                init_characters(gs.party);
                memset(gs.inv, 0, sizeof(gs.inv));
                gs.inv[ITEM_POTION] = 2;
                gs.inv[ITEM_ETHER] = 1;
            }
        }
        else if (cell == 'B') {
            Enemy boss = make_boss_enemy();

            int win = battle(&gs, boss);
            if (win) {
                gs.game_clear = 1;
                show_ending();
                break;
            }
            else {
                clear_screen();
                printf(RED "マスタードラゴンに敗北した…\n" RESET);
                printf("Enterでタイトルへ...");
                read_line(buf, sizeof(buf));

                show_title();
                load_map_template(gs.map);
                gs.px = 1; gs.py = 1;
                init_characters(gs.party);
                memset(gs.inv, 0, sizeof(gs.inv));
                gs.inv[ITEM_POTION] = 2;
                gs.inv[ITEM_ETHER] = 1;
            }
        }
    }

    return 0;
}

srand((unsigned)time(NULL));

GameState gs;
memset(&gs, 0, sizeof(gs));

extern const ItemDef g_items[ITEM_COUNT];

const ItemDef g_items[ITEM_COUNT] = { ... };