diff --git a/src/cart.c b/src/cart.c
index a73ffeb..2b25940 100644
--- a/src/cart.c
+++ b/src/cart.c
@@ -19,7 +19,7 @@ int nes_cart_init_mem(nes_cart* cart, void* mem, int len) {
 
     if (0 == status) {
         int prg_size = ines_prg_rom_chunk * hdr->prg_size_lsb;
-        if (prg_size > nes_mem_rom_size || prg_size <= 0) {
+        if (prg_size <= 0) {
             INES_ERR("Bad program ROM size: %d / %d",
                      prg_size, nes_mem_rom_size);
             status = -1;
@@ -32,19 +32,10 @@ int nes_cart_init_mem(nes_cart* cart, void* mem, int len) {
 
     if (0 == status) {
         int chr_size = ines_chr_rom_chunk * hdr->chr_size_lsb;
-        if (chr_size > nes_ppu_mem_size || chr_size <= 0) {
-            INES_ERR("Bad sprite ROM size: %d / %d",
-                     chr_size, nes_ppu_mem_size);
-            status = -1;
-
-        } else {
-            cart->chr_rom = ptr;
-            cart->chr_rom_size = chr_size;
-        }
+        cart->chr_rom = ptr;
+        cart->chr_rom_size = chr_size;
         ptr += chr_size;
-    }
 
-    if (0 == status) {
         int index = (hdr->flags_6 & ines_Mapper_Nibble_Lo) >> 4 |
                     (hdr->flags_7 & ines_Mapper_Nibble_Hi);
         cart->mapper = nes_mappers[index];
diff --git a/src/cart.h b/src/cart.h
index 334fe27..bb6c757 100644
--- a/src/cart.h
+++ b/src/cart.h
@@ -5,9 +5,6 @@
 #include <stdio.h>
 
 
-#define nes_mem_wram_size   (0x2000U)
-
-
 typedef enum {
     Cart_Flag_Vertical   = 0b0,
     Cart_Flag_Horizontal = 0b1,
@@ -18,7 +15,6 @@ typedef struct nes_cart_t {
     int prg_rom_size;
     uint8_t* chr_rom;
     int chr_rom_size;
-    uint8_t wram[nes_mem_wram_size];
     nes_Cart_Flags flags;
     struct nes_mapper_t* mapper;
 
diff --git a/src/map/map.h b/src/map/map.h
index a98997c..4a493f1 100644
--- a/src/map/map.h
+++ b/src/map/map.h
@@ -1,2 +1,2 @@
+#include "../nes.h"
 #include "../mapper.h"
-#include "../cart.h"
diff --git a/src/map/mmc1.c b/src/map/mmc1.c
index 98da90a..2e71a90 100644
--- a/src/map/mmc1.c
+++ b/src/map/mmc1.c
@@ -1,72 +1,214 @@
+#include <stdlib.h>
+
 #include "map.h"
 
 
+#define MAP_LOG(fmt, ...) //printf("MAP: " fmt "\n" __VA_OPT__(,) __VA_ARGS__)
+
+
 typedef struct {
+    // TODO: Does this even support CHR ROM?
     uint8_t* prg_rom;
     int prg_rom_size;
-    uint8_t* prg_ram;
-    int prg_ram_size;
-    uint8_t* chr_rom;
-    int chr_rom_size;
 
     uint8_t reg_shift;
+    uint8_t reg_n_shift;
     uint8_t reg_control;
     uint8_t reg_chr_0;
     uint8_t reg_chr_1;
     uint8_t reg_prg;
+
+    uint8_t* chr_bank[2];
+    uint8_t* vram_bank[4];
+    uint8_t* prg_bank[2];
+
+    uint8_t vram[2][nes_vram_page_size];
+    uint8_t chr[32][nes_chr_page_size];
+    uint8_t wram[nes_mem_wram_size];
 } mmc1_mapper;
 
-/*
-int mmc1_init(nes_mapper* nes_map, nes_cart* cart) {
-    nrom_mapper* map = malloc(sizeof(nrom_mapper));
+
+static void mmc1_update_vram(mmc1_mapper* map) {
+    // VRAM selection
+    int nametable = (map->reg_control & 0b11);
+    if (nametable == 0) {
+        MAP_LOG("VRAM: 1-screen, lower bank");
+        map->vram_bank[0] = map->vram_bank[1] =
+            map->vram_bank[2] = map->vram_bank[3] =
+                map->vram[0];
+    } else if (nametable == 1) {
+        MAP_LOG("VRAM: 1-screen, upper bank");
+        map->vram_bank[0] = map->vram_bank[1] =
+            map->vram_bank[2] = map->vram_bank[3] =
+                map->vram[1];
+    } else if (nametable == 2) {
+        MAP_LOG("VRAM: Vertical mirroring");
+        map->vram_bank[0] = map->vram_bank[2] = map->vram[0];
+        map->vram_bank[1] = map->vram_bank[3] = map->vram[1];
+    } else if (nametable == 3) {
+        MAP_LOG("VRAM: Horizontal mirroring");
+        map->vram_bank[0] = map->vram_bank[1] = map->vram[0];
+        map->vram_bank[2] = map->vram_bank[3] = map->vram[1];
+    }
+}
+
+static void mmc1_update_chr(mmc1_mapper* map) {
+    // CHR RAM selection
+    if (!(map->reg_control & 0b10000)) {
+        int bank = (map->reg_chr_0 & 0b11110);
+        MAP_LOG("CHR: 8 KB: %d + %d", bank, bank + 1);
+        map->chr_bank[0] = map->chr[bank];
+        map->chr_bank[1] = map->chr[bank + 1];
+    } else {
+        MAP_LOG("CHR: %d + %d", map->reg_chr_0, map->reg_chr_1);
+        map->chr_bank[0] = map->chr[map->reg_chr_0];
+        map->chr_bank[1] = map->chr[map->reg_chr_1];
+    }
+}
+
+static void mmc1_update_prg(mmc1_mapper* map) {
+    // PRG ROM selection
+    int mode = (map->reg_control >> 2) & 3;
+    int bank = (map->reg_prg & 0b01111);
+    if (!(mode & 0b10)) {
+        bank = (bank & 0b01110);
+        MAP_LOG("PRG: 32 KB %d + %d", bank, bank + 1);
+        bank *= nes_prg_rom_page_size;
+        map->prg_bank[0] = &map->prg_rom[bank];
+        map->prg_bank[1] = &map->prg_rom[bank +
+                                         nes_prg_rom_page_size];
+    } else if (mode == 2) {
+        MAP_LOG("PRG: %d + %d", 0, bank);
+        bank *= nes_prg_rom_page_size;
+        map->prg_bank[0] = &map->prg_rom[0];
+        map->prg_bank[1] = &map->prg_rom[bank];
+    } else if (mode == 3) {
+        MAP_LOG("PRG: %d + %d", bank, (map->prg_rom_size /
+                                       nes_prg_rom_page_size) - 1);
+        bank *= nes_prg_rom_page_size;
+        map->prg_bank[0] = &map->prg_rom[bank];
+        map->prg_bank[1] = &map->prg_rom[map->prg_rom_size -
+                                         nes_prg_rom_page_size];
+    }
+}
+
+static void mmc1_reset(nes_mapper* nes_map) {
+    mmc1_mapper* map = (mmc1_mapper*)nes_map->data;
+    map->reg_shift   = 0b10000;
+    map->reg_control = 0;
+    map->reg_chr_0   = 0;
+    map->reg_chr_1   = 0;
+    map->reg_prg     = 0;
+    mmc1_update_prg(map);
+    mmc1_update_chr(map);
+    mmc1_update_vram(map);
+}
+
+static int mmc1_init(nes_mapper* nes_map, nes_cart* cart) {
+    mmc1_mapper* map = calloc(1, sizeof(mmc1_mapper));
     nes_map->data = map;
     if (NULL != map) {
         map->prg_rom      = cart->prg_rom;
         map->prg_rom_size = cart->prg_rom_size;
-        map->chr_rom      = cart->chr_rom;
-        map->chr_rom_size = cart->chr_rom_size;
-        map->prg_ram      = cart->wram;
-        map->prg_ram_size = nes_mem_wram_size;
-
-        map->shift_reg = 0;
+        mmc1_reset(nes_map);
     }
     return (NULL == map ? -1 : 0);
 }
 
-void nrom_done(nes_mapper* nes_map) {
+static void mmc1_done(nes_mapper* nes_map) {
     free(nes_map->data);
 }
 
-static inline uint8_t* nrom_prg_addr(nrom_mapper* map,
+static inline uint8_t* mmc1_prg_addr(mmc1_mapper* map,
                                      uint16_t addr) {
-    if (addr > map->prg_rom_size) {
-        addr &= 0x3FFF;
+    int bank = (addr >> 14) & 1;
+    addr &= 0x3FFFU;
+    return &map->prg_bank[bank][addr];
+}
+
+static inline uint8_t* mmc1_wram_addr(mmc1_mapper* map,
+                                      uint16_t addr) {
+    return &(map->wram[addr & 0x1FFFU]);
+}
+
+static uint8_t mmc1_read(nes_mapper* map, uint16_t addr) {
+    uint8_t val = 0;
+    if (addr >= nes_mem_rom_start) {
+        val = *(mmc1_prg_addr((mmc1_mapper*)map->data, addr));
+    } else if (addr >= nes_mem_wram_start) {
+        val = *(mmc1_wram_addr((mmc1_mapper*)map->data, addr));
     }
-    return &(map->prg_rom[addr]);
+    return val;
 }
 
-uint8_t nrom_prg_read(nes_mapper* map, uint16_t addr) {
-    return *(nrom_prg_addr((nrom_mapper*)map->data, addr));
+static void mmc1_write(nes_mapper* nes_map,
+                       uint16_t addr, uint8_t val) {
+    mmc1_mapper* map = (mmc1_mapper*)nes_map->data;
+    if (addr >= nes_mem_rom_start) {
+        MAP_LOG("Write $%04x < %02x", addr, val);
+        if (val & 0x80U) {
+            MAP_LOG("Resetting");
+            map->reg_shift = 0b10000;
+            map->reg_control |= 0b01100;
+            mmc1_update_prg(map);
+        } else {
+            // TODO: Handle consective-cycle writes?
+            int done = (map->reg_shift & 1);
+            map->reg_shift = (map->reg_shift >> 1) |
+                             ((val & 1) << 4);
+            if (done) {
+                int reg = (addr >> 13) & 0b11;
+                if (reg == 0) {
+                    MAP_LOG("Control %02x", map->reg_shift);
+                    map->reg_control = map->reg_shift;
+                    mmc1_update_chr(map);
+                    mmc1_update_vram(map);
+                    mmc1_update_prg(map);
+                } else if (reg == 1) {
+                    MAP_LOG("CHR_0 %02x", map->reg_shift);
+                    map->reg_chr_0 = map->reg_shift;
+                    mmc1_update_chr(map);
+                } else if (reg == 2) {
+                    MAP_LOG("CHR_1 %02x", map->reg_shift);
+                    map->reg_chr_1 = map->reg_shift;
+                    mmc1_update_chr(map);
+                } else {
+                    MAP_LOG("PRG %02x", map->reg_shift);
+                    map->reg_prg = map->reg_shift;
+                    mmc1_update_prg(map);
+                }
+                map->reg_shift = 0b10000;
+            }
+        }
+
+    } else if ( addr < nes_mem_rom_start &&
+                addr >= nes_mem_wram_start) {
+        *(mmc1_wram_addr(map, addr)) = val;
+    }
 }
 
-void nrom_prg_write(nes_mapper* map, uint16_t addr, uint8_t val) {
-    // No ROM writes.
+static uint8_t* mmc1_chr_addr(nes_mapper* nes_map,
+                              uint16_t addr) {
+    int page = (addr >> 12) & 1;
+    addr &= 0xFFFU;
+    return &((mmc1_mapper*)nes_map->data)->chr_bank[page][addr];
 }
 
-uint8_t* nrom_chr_addr(nes_mapper* nes_map, uint16_t addr) {
-    nrom_mapper* map = (nrom_mapper*)nes_map->data;
-    return &map->chr_rom[addr % map->chr_rom_size];
+static uint8_t* mmc1_vram_addr(nes_mapper* nes_map,
+                               uint16_t addr) {
+    int page = (addr >> 10) & 3;
+    int loc = addr & 0x3FFU;
+//    MAP_LOG("VRAM $%04x -> %p", addr, ((mmc1_mapper*)nes_map->data)->vram_bank[page]);
+    return &((mmc1_mapper*)nes_map->data)->vram_bank[page][loc];
 }
 
-*/
 
 nes_mapper mapper_mmc1 = {
-/*
     .init = mmc1_init,
+    .reset = mmc1_reset,
     .done = mmc1_done,
-    .prg_read = mmc1_prg_read,
-    .prg_write = mmc1_prg_write,
+    .read = mmc1_read,
+    .write = mmc1_write,
     .chr_addr = mmc1_chr_addr,
-    .vram_addr = mmc1_chr_addr,
-*/
+    .vram_addr = mmc1_vram_addr,
 };
diff --git a/src/map/nrom.c b/src/map/nrom.c
index 0bdf44e..23937da 100644
--- a/src/map/nrom.c
+++ b/src/map/nrom.c
@@ -6,16 +6,17 @@
 typedef struct {
     uint8_t* prg_rom;
     int prg_rom_size;
-    uint8_t* prg_ram;
-    int prg_ram_size;
     uint8_t* chr_rom;
     int chr_rom_size;
     uint8_t mirror;
     uint8_t vram[nes_vram_page_size * 2];
+    uint8_t wram[nes_mem_wram_size];
 } nrom_mapper;
 
 
-int nrom_init(nes_mapper* nes_map, nes_cart* cart) {
+static void nrom_reset(nes_mapper* nes_map) {}
+
+static int nrom_init(nes_mapper* nes_map, nes_cart* cart) {
     nrom_mapper* map = calloc(1, sizeof(nrom_mapper));
     nes_map->data = map;
     if (NULL != map) {
@@ -23,39 +24,54 @@ int nrom_init(nes_mapper* nes_map, nes_cart* cart) {
         map->prg_rom_size = cart->prg_rom_size;
         map->chr_rom      = cart->chr_rom;
         map->chr_rom_size = cart->chr_rom_size;
-        map->prg_ram      = cart->wram;
-        map->prg_ram_size = nes_mem_wram_size;
         map->mirror = (cart->flags & Cart_Flag_Horizontal) ? 0 : 1;
     }
     return (NULL == map ? -1 : 0);
 }
 
-void nrom_done(nes_mapper* nes_map) {
+static void nrom_done(nes_mapper* nes_map) {
     free(nes_map->data);
 }
 
 static inline uint8_t* nrom_prg_addr(nrom_mapper* map,
                                      uint16_t addr) {
+    addr &= 0x7FFFU;
     if (addr > map->prg_rom_size) {
         addr &= 0x3FFF;
     }
     return &(map->prg_rom[addr]);
 }
 
-uint8_t nrom_prg_read(nes_mapper* map, uint16_t addr) {
-    return *(nrom_prg_addr((nrom_mapper*)map->data, addr));
+static inline uint8_t* nrom_wram_addr(nrom_mapper* map,
+                                     uint16_t addr) {
+    return &(map->wram[addr & 0x1FFFU]);
+}
+
+static uint8_t nrom_read(nes_mapper* map, uint16_t addr) {
+    uint8_t val = 0;
+    if (addr >= nes_mem_rom_start) {
+        val = *(nrom_prg_addr((nrom_mapper*)map->data, addr));
+    } else if (addr >= nes_mem_wram_start) {
+        val = *(nrom_wram_addr((nrom_mapper*)map->data, addr));
+    }
+    return val;
 }
 
-void nrom_prg_write(nes_mapper* map, uint16_t addr, uint8_t val) {
-    // No ROM writes.
+static void nrom_write(nes_mapper* map,
+                       uint16_t addr, uint8_t val) {
+    if (addr < nes_mem_rom_start && addr >= nes_mem_wram_start) {
+        *(nrom_wram_addr((nrom_mapper*)map->data, addr)) = val;
+    }
 }
 
-uint8_t* nrom_chr_addr(nes_mapper* nes_map, uint16_t addr) {
+static uint8_t* nrom_chr_addr(nes_mapper* nes_map,
+                              uint16_t addr) {
     nrom_mapper* map = (nrom_mapper*)nes_map->data;
     return &map->chr_rom[addr % map->chr_rom_size];
 }
 
-uint8_t* nrom_vram_addr(nes_mapper* nes_map, uint16_t addr) {
+static uint8_t* nrom_vram_addr(nes_mapper* nes_map,
+                               uint16_t addr) {
     nrom_mapper* map = (nrom_mapper*)nes_map->data;
     int page = addr >> 10U;
     page >>= map->mirror;
@@ -65,9 +81,10 @@ uint8_t* nrom_vram_addr(nes_mapper* nes_map, uint16_t addr) {
 
 nes_mapper mapper_nrom = {
     .init = nrom_init,
+    .reset = nrom_reset,
     .done = nrom_done,
-    .prg_read = nrom_prg_read,
-    .prg_write = nrom_prg_write,
+    .read = nrom_read,
+    .write = nrom_write,
     .chr_addr = nrom_chr_addr,
     .vram_addr = nrom_vram_addr,
 };
diff --git a/src/mapper.h b/src/mapper.h
index 3c0e01f..3b82a52 100644
--- a/src/mapper.h
+++ b/src/mapper.h
@@ -4,17 +4,19 @@
 #include <stdint.h>
 
 
-#define nes_chr_page_size   (0x1000U)
-#define nes_vram_page_size  (0x0400U)
+#define nes_chr_page_size       (0x1000U)
+#define nes_vram_page_size      (0x0400U)
+#define nes_prg_rom_page_size   (0x4000U)
 
 
 struct nes_cart_t;
 
 typedef struct nes_mapper_t {
     int (*init)(struct nes_mapper_t*, struct nes_cart_t* cart);
+    void (*reset)(struct nes_mapper_t*);
     void (*done)(struct nes_mapper_t*);
-    uint8_t (*prg_read)(struct nes_mapper_t*, uint16_t addr);
-    void (*prg_write)(struct nes_mapper_t*, uint16_t addr, uint8_t val);
+    uint8_t (*read)(struct nes_mapper_t*, uint16_t addr);
+    void (*write)(struct nes_mapper_t*, uint16_t addr, uint8_t val);
     uint8_t* (*chr_addr)(struct nes_mapper_t*, uint16_t addr);
     uint8_t* (*vram_addr)(struct nes_mapper_t*, uint16_t addr);
     void* data;
@@ -25,19 +27,23 @@ static inline int nes_map_init(nes_mapper* map,
     return map->init(map, cart);
 }
 
+static inline void nes_map_reset(nes_mapper* map) {
+    map->reset(map);
+}
+
 static inline void nes_map_done(nes_mapper* map) {
     map->done(map);
 }
 
-static inline uint8_t nes_map_prg_read(nes_mapper* map,
+static inline uint8_t nes_map_read(nes_mapper* map,
                                        uint16_t addr) {
-    return map->prg_read(map, addr);
+    return map->read(map, addr);
 }
 
-static inline void nes_map_prg_write(nes_mapper* map,
+static inline void nes_map_write(nes_mapper* map,
                                      uint16_t addr,
                                      uint8_t val) {
-    map->prg_write(map, addr, val);
+    map->write(map, addr, val);
 }
 
 static inline uint8_t* nes_map_chr_addr(nes_mapper* map,
diff --git a/src/nes.c b/src/nes.c
index aeb6993..b3e312b 100644
--- a/src/nes.c
+++ b/src/nes.c
@@ -22,16 +22,8 @@ uint8_t nes_mem_read(nes* sys, uint16_t addr) {
     } else if (addr < nes_mem_exp_start) {
         val = nes_apu_read(&sys->apu, addr);
 
-    } else if (addr < nes_mem_wram_start) {
-        // TODO: Expansion ROM support
-
-    } else if (addr < nes_mem_rom_start) {
-        // TODO: Send to mapper?
-        val = sys->cart.wram[addr - nes_mem_wram_start];
-
     } else {
-        val = nes_map_prg_read(sys->cart.mapper,
-                               addr - nes_mem_rom_start);
+        val = nes_map_read(sys->cart.mapper, addr);
     }
 
     return val;
@@ -61,15 +53,8 @@ void nes_mem_write(nes* sys, uint16_t addr, uint8_t val) {
     } else if (addr < nes_mem_exp_start) {
         nes_apu_write(&sys->apu, addr, val);
 
-    } else if (addr < nes_mem_wram_start) {
-        // No ROM writes
-
-    } else if (addr < nes_mem_rom_start) {
-        sys->cart.wram[addr - nes_mem_wram_start] = val;
-
     } else {
-        nes_map_prg_write(sys->cart.mapper,
-                          addr - nes_mem_rom_start, val);
+        nes_map_write(sys->cart.mapper, addr, val);
     }
 }
 
diff --git a/src/nes.h b/src/nes.h
index dcd654d..5b95dc8 100644
--- a/src/nes.h
+++ b/src/nes.h
@@ -23,7 +23,7 @@
 #define nes_mem_exp_start   (0x4020U)
 #define nes_mem_exp_size    (0x1FE0U)
 #define nes_mem_wram_start  (0x6000U)
-//#define nes_mem_wram_size   (0x2000U)
+#define nes_mem_wram_size   (0x2000U)
 #define nes_mem_rom_start   (0x8000U)
 #define nes_mem_rom_size    (0x8000U)
 
diff --git a/src/ppu.c b/src/ppu.c
index 73c7207..2a416a4 100644
--- a/src/ppu.c
+++ b/src/ppu.c
@@ -159,6 +159,10 @@ void nes_ppu_write(nes_ppu* ppu, uint16_t addr, uint8_t val) {
 #endif // DEBUG_VRAM
 //            printf("PPU: VRAM %04x < %02x\n", vram_addr, val);
             nes_vram_write(ppu->mapper, vram_addr, val);
+
+        } else {
+//            printf("PPU: CHR MEM WRITE %04x > %02x\n", ppu->addr, val);
+            *(nes_map_chr_addr(ppu->mapper, ppu->addr)) = val;
         }
 
         ppu->addr += (ppu->control & ppu_Control_VRAM_Inc) ?