path: root/src/sequencer.c

#define SPRITE_NOTE_NAMES_W 16
#define SPRITE_NOTE_NAMES_H 8

u32 sprite_note_names[] = {
    0x000000e0, 0x202020e0, 0x0000000e, 0x080e020e,
    0x00000098, 0xa8a8a898, 0x00000038, 0x203b0a39,
    0x00000060, 0xa0a0a060, 0x0000000e, 0x080e020e,
    0x000000b8, 0x889888b8, 0x00000038, 0x203b0a39,
    0x000000e0, 0x206020e0, 0x0000000e, 0x080e020e,
    0x000000e0, 0x20602020, 0x0000000e, 0x080e020e,
    0x000000b8, 0x8888a8b8, 0x00000038, 0x203b0a39,
    0x000000e0, 0x2020a0e0, 0x0000000e, 0x080e020e,
    0x000000b8, 0xa8a8b8a8, 0x00000038, 0x203b0a39,
    0x000000e0, 0xa0a0e0a0, 0x0000000e, 0x080e020e,
    0x000000b8, 0xa898a8b8, 0x00000038, 0x203b0a39,
    0x000000e0, 0xa060a0e0, 0x0000000e, 0x080e020e,
    0x000000e0, 0x202020e0, 0x0000000e, 0x080c080e,
    0x00000098, 0xa8a8a898, 0x00000038, 0x20332239,
    0x00000060, 0xa0a0a060, 0x0000000e, 0x080c080e,
    0x000000b8, 0x889888b8, 0x00000038, 0x20332239,
    0x000000e0, 0x206020e0, 0x0000000e, 0x080c080e,
    0x000000e0, 0x20602020, 0x0000000e, 0x080c080e,
    0x000000b8, 0x8888a8b8, 0x00000038, 0x20332239,
    0x000000e0, 0x2020a0e0, 0x0000000e, 0x080c080e,
    0x000000b8, 0xa8a8b8a8, 0x00000038, 0x20332239,
    0x000000e0, 0xa0a0e0a0, 0x0000000e, 0x080c080e,
    0x000000b8, 0xa898a8b8, 0x00000038, 0x20332239,
    0x000000e0, 0xa060a0e0, 0x0000000e, 0x080c080e,
    0x000000e0, 0x202020e0, 0x00000008, 0x0c0a0e08,
    0x00000098, 0xa8a8a898, 0x00000020, 0x302b3a21,
    0x00000060, 0xa0a0a060, 0x00000008, 0x0c0a0e08,
    0x000000b8, 0x889888b8, 0x00000020, 0x302b3a21,
    0x000000e0, 0x206020e0, 0x00000008, 0x0c0a0e08,
    0x000000e0, 0x20602020, 0x00000008, 0x0c0a0e08,
    0x000000b8, 0x8888a8b8, 0x00000020, 0x302b3a21,
    0x000000e0, 0x2020a0e0, 0x00000008, 0x0c0a0e08,
    0x000000b8, 0xa8a8b8a8, 0x00000020, 0x302b3a21,
    0x000000e0, 0xa0a0e0a0, 0x00000008, 0x0c0a0e08,
    0x000000b8, 0xa898a8b8, 0x00000020, 0x302b3a21,
    0x000000e0, 0xa060a0e0, 0x00000008, 0x0c0a0e08,
    0x000000e0, 0x202020e0, 0x0000000e, 0x020e080e,
    0x00000098, 0xa8a8a898, 0x00000038, 0x083b2239,
    0x00000060, 0xa0a0a060, 0x0000000e, 0x020e080e,
    0x000000b8, 0x889888b8, 0x00000038, 0x083b2239,
    0x000000e0, 0x206020e0, 0x0000000e, 0x020e080e,
    0x000000e0, 0x20602020, 0x0000000e, 0x020e080e,
    0x000000b8, 0x8888a8b8, 0x00000038, 0x083b2239,
    0x000000e0, 0x2020a0e0, 0x0000000e, 0x020e080e,
    0x000000b8, 0xa8a8b8a8, 0x00000038, 0x083b2239,
    0x000000e0, 0xa0a0e0a0, 0x0000000e, 0x020e080e,
    0x000000b8, 0xa898a8b8, 0x00000038, 0x083b2239,
    0x000000e0, 0xa060a0e0, 0x0000000e, 0x020e080e,
    0x000000e0, 0x202020e0, 0x0000000e, 0x020e0a0e,
    0x00000098, 0xa8a8a898, 0x00000038, 0x083b2a39,
    0x00000060, 0xa0a0a060, 0x0000000e, 0x020e0a0e,
    0x000000b8, 0x889888b8, 0x00000038, 0x083b2a39,
    0x000000e0, 0x206020e0, 0x0000000e, 0x020e0a0e,
    0x000000e0, 0x20602020, 0x0000000e, 0x020e0a0e,
    0x000000b8, 0x8888a8b8, 0x00000038, 0x083b2a39,
    0x000000e0, 0x2020a0e0, 0x0000000e, 0x020e0a0e,
    0x000000b8, 0xa8a8b8a8, 0x00000038, 0x083b2a39,
    0x000000e0, 0xa0a0e0a0, 0x0000000e, 0x020e0a0e,
    0x000000b8, 0xa898a8b8, 0x00000038, 0x083b2a39,
    0x000000e0, 0xa060a0e0, 0x0000000e, 0x020e0a0e,
    0x000000e0, 0x202020e0, 0x0000000e, 0x08040202,
    0x00000098, 0xa8a8a898, 0x00000038, 0x20130a09,
    0x00000060, 0xa0a0a060, 0x0000000e, 0x08040202,
    0x000000b8, 0x889888b8, 0x00000038, 0x20130a09,
    0x000000e0, 0x206020e0, 0x0000000e, 0x08040202,
    0x000000e0, 0x20602020, 0x0000000e, 0x08040202,
    0x000000b8, 0x8888a8b8, 0x00000038, 0x20130a09,
    0x000000e0, 0x2020a0e0, 0x0000000e, 0x08040202,
    0x000000b8, 0xa8a8b8a8, 0x00000038, 0x20130a09,
    0x000000e0, 0xa0a0e0a0, 0x0000000e, 0x08040202,
    0x000000b8, 0xa898a8b8, 0x00000038, 0x20130a09,
    0x000000e0, 0xa060a0e0, 0x0000000e, 0x08040202,
    0x000000e0, 0x202020e0, 0x0000000e, 0x0a0e0a0e,
};

u32 sprite_trigger_button[] = {
    0xfe020202, 0x02020202, 0xff808080, 0x80808080,
    0x02020202, 0x02020202, 0x80808080, 0x80808080,
    0x02020202, 0x020202fe, 0x80808080, 0x808080ff,
    0x00000000, 0x00000000, 0x00000000, 0x00000000,
};

u32 sprite_trigger_active_indicator[] = {
    0x00000000, 0x00f80000,
};

u32 sprite_trigger_selection[] = {
    0x0f010101, 0x00000000, 0x80000000, 0x00000000,
    0x07040404, 0x00000000, 0x00000000, 0x00000000,
    0x00000000, 0x00000000, 0x00000000, 0x00000000,
    0x00000000, 0x00000000, 0x00000000, 0x00000000,
    0x00000000, 0x00000000, 0x00000000, 0x00000000,
    0x00000000, 0x00000000, 0x00000000, 0x00000000,
    0x0101010f, 0x00000000, 0x00000080, 0x00000000,
    0x04040407, 0x00000000, 0x00000000, 0x00000000,
};

u32 sprite_env_label_volume[] = {
    0xa0a0a0a0, 0xc0000000, 0x262a2a2a, 0xee000000,
    0xaaeaaaaa, 0xae000000, 0x0e020602, 0x0e000000,
};

u32 sprite_env_label_time[] = {
    0x00000000, 0x00000000, 0xee444444, 0xe4000000,
    0xea2e6a2a, 0xea000000, 0x00000000, 0x00000000,
};

u32 sprite_env_label_direction[] = {
    0x00000000, 0x00000000, 0xcc949494, 0xcc000000,
    0x1d140cd4, 0xd5000000, 0x00000000, 0x00000000,
};

u32 sprite_env_label_env[] = {
    0x6ea2a6a2, 0xae000000, 0xea2a6a2a, 0xec000000,
    0x62a2a2a2, 0xee000000, 0xee2a6e22, 0xe2000000,
};

u32 sprite_env_volume[] = {
    0x80808080, 0x80808000, 0x0f0c0c0c, 0x0c6c6f00,
    0x1f999919, 0x19999f00, 0x00090d06, 0x030d0c00,
    0x80808080, 0x80808000, 0x0f01010f, 0x09696f00,
    0x1f83831f, 0x13939f00, 0x00090d06, 0x030d0c00,
    0x60606060, 0x60606000, 0x1f18181e, 0x18d8df00,
    0x3e30303c, 0x30303e00, 0x00131b0c, 0x061b1900,
    0xf8c0c0f8, 0x1818f800, 0x3e06063e, 0x26a6be00,
    0x7c0c0c7c, 0x4c4d7d00, 0x00263618, 0x0c363200,
    0xf8c0c0f8, 0x1818f800, 0x3e323232, 0x32b2be00,
    0x7c646464, 0x64657d00, 0x00263618, 0x0c363200,
    0xf8c0c0f0, 0xc0c0f800, 0x3e30303c, 0x30b0be00,
    0x7c606078, 0x60617d00, 0x00263618, 0x0c363200,
    0xc0e0d0c8, 0xf8c0c000, 0x3e323232, 0x32b2be00,
    0x7c646464, 0x64657d00, 0x00263618, 0x0c363200,
    0xc0e0d0c8, 0xf8c0c000, 0x3e06063e, 0x26a6be00,
    0x7c0c0c7c, 0x4c4d7d00, 0x00263618, 0x0c363200,
    0xf81818f8, 0xc0c0f800, 0x3e30303c, 0x30b0be00,
    0x7c606078, 0x60617d00, 0x00263618, 0x0c363200,
    0xf81818f8, 0x9898f800, 0x3e323232, 0x32b2be00,
    0x7c646464, 0x64657d00, 0x00263618, 0x0c363200,
    0xf81818f8, 0x9898f800, 0x3e06063e, 0x26a6be00,
    0x7c0c0c7c, 0x4c4d7d00, 0x00263618, 0x0c363200,
    0xf8c0c060, 0x30181800, 0x3e30303c, 0x30b0be00,
    0x7c606078, 0x60617d00, 0x00263618, 0x0c363200,
    0xf8c8c8f8, 0xc8c8f800, 0x3e323232, 0x32b2be00,
    0x7c646464, 0x64657d00, 0x00263618, 0x0c363200,
    0xf8c8c8f8, 0xc8c8f800, 0x3e06063e, 0x26a6be00,
    0x7c0c0c7c, 0x4c4d7d00, 0x00263618, 0x0c363200,
    0xf8c8c8f8, 0xc0c0f800, 0x3e30303c, 0x30b0be00,
    0x7c606078, 0x60617d00, 0x00263618, 0x0c363200,
    0xec2c2c2c, 0x2c2cec00, 0xfbcbcbcb, 0xcbcbfb00,
    0xf0909090, 0x9096f600, 0x0199d961, 0x31d9c900,
};

u32 sprite_env_time[] = {
    0x80808080, 0x80808000, 0x0f0c0c0c, 0x0c6c6f00,
    0x1f999919, 0x19999f00, 0x00090d06, 0x030d0c00,
    0x60606060, 0x60606000, 0x181c1a19, 0x1fd8d800,
    0x3e30303c, 0x30303e00, 0x00131b0c, 0x061b1900,
    0xf8c0c0f8, 0x1818f800, 0x3e32323e, 0x32b2be00,
    0x7c0c0c7c, 0x4c4d7d00, 0x00263618, 0x0c363200,
    0xc0e0d0c8, 0xf8c0c000, 0x3e30303e, 0x0686be00,
    0x7c64647c, 0x60617d00, 0x00263618, 0x0c363200,
    0xe06060e0, 0x0000e000, 0xfbc0c063, 0x331b1b00,
    0x30303030, 0x30363600, 0x00131b0c, 0x061b1900,
    0xe0000080, 0xc0606000, 0x1b1b1b19, 0x18d8d800,
    0x30383432, 0x3e303000, 0x00131b0c, 0x061b1900,
    0xf8c8c8f8, 0xc8c8f800, 0x3e06063e, 0x30b0be00,
    0x7c606030, 0x180d0d00, 0x00263618, 0x0c363200,
    0xec2c2c2c, 0x2c2cec00, 0xfbcbcbcb, 0xcbcbfb00,
    0xf0909090, 0x9096f600, 0x0199d961, 0x31d9c900,
};

u32 sprite_env_sweep_direction[] = {
    0x00000000, 0x00000000, 0xc8c8c8c8, 0xc8c8f800,
    0x3e32323e, 0x02020200, 0x00000000, 0x00000000,
    0xe0202020, 0x2020e000, 0x71cbcbcb, 0xcbcb7100,
    0xb2b2b2b2, 0xb2ba9400, 0x0d0f0e0c, 0x0c0c0c00,
};

typedef struct SeqTrigger {
    bool trigger;
    Note note;
    u8 env_volume;
    u8 env_time;
    u8 env_direction;
    // TODO: ...
} SeqTrigger;

static SeqTrigger sequence_synth[] = {
    {true  , NOTE_D_4       , 0, 0, 0},
    {true  , NOTE_F_4       , 1, 1, 0},
    {true  , NOTE_A_4       , 2, 2, 0},
    {true  , NOTE_C_5       , 3, 3, 0},

    {true  , NOTE_D_4       , 4, 4, 1},
    {false , NOTE_C_SHARP_4 , 5, 5, 1},
    {false , NOTE_D_4       , 6, 6, 1},
    {false , NOTE_D_4       , 7, 7, 1},

    {true  , NOTE_D_4       , 8, 0, 0},
    {true  , NOTE_F_4       , 9, 1, 0},
    {true  , NOTE_A_4       , 10, 2, 0},
    {true  , NOTE_C_5       , 11, 3, 0},

    {true  , NOTE_D_4       , 12, 4, 1},
    {false , NOTE_D_4       , 13, 5, 1},
    {true  , NOTE_A_4       , 14, 6, 1},
    {false , NOTE_A_5       , 15, 7, 1},
};

static int bpm = 120;
static int step_counter = 0;
static Note active_note;

void
irq_timer_0(void) {
    SeqTrigger *trig = &sequence_synth[step_counter];
    active_note = trig->note;
    if (trig->trigger) {
        SOUND_SQUARE1_CTRL = SOUND_SQUARE_ENV_VOL(trig->env_volume)
            | SOUND_SQUARE_ENV_TIME(trig->env_time)
            | SOUND_SQUARE_ENV_INC(trig->env_direction)
            | SOUND_SQUARE_DUTY(2);
        SOUND_SQUARE1_FREQ = SOUND_SQUARE_RESET | sound_rates[active_note];
    }
    step_counter = (step_counter + 1) % 16;
}

void
set_time(int bpm) {
    // The number of ticks of a 1024 cycle clock in a step based on the BPM can
    // be calculated as:
    //     X bpm -> 60000 / 4 / bpm = Y ms = Ye-3 s
    //     Y ms  -> Ye-3 / 59.99e-9 /1024 = Z ticks
    // We have to operate on integer values, so the numbers have been
    // precalculated to `n_ticks = 244181 / bmp`
    int n_ticks = -244181 / bpm;

    irs_set(IRQ_TIMER_0, irq_timer_0);
    TIMER_DATA_0 = n_ticks;
    TIMER_CTRL_0 = TIMER_CTRL_IRQ | TIMER_CTRL_ENABLE | TIMER_CTRL_FREQ_3;
}

//
// Sequencer sprite memory.
//
// Currently we load all sequencer sprite memory in the VRAM:
//
// - Note names: 73x2 tiles.
// - Sprite trigger button: 8 tiles.
// - Current step marker: 1 tile.
// - Selected trigger marker: 16 tile.
// - Env: Volume label: 4 tiles.
// - Env: Volume text: 16x4 tiles
// - Env: Time label: 4 tiles.
// - Env: Time text: 8x4 tiles
// - Env: Direction label: 4 tiles.
// - Env: Direction text: 2x4 tiles
//
// The order of OBJs correspond to:
//
// - 000-015 step note names.
// - 015-031 step trigger steps.
// - 032-032 current step marker.
// - 033-033 trigger selection indicator.
// - 034-034 envelope: volume label.
// - 035-035 envelope: volume indicator.
// - 036-036 envelope: time label.
// - 037-037 envelope: time indicator.
// - 038-038 envelope: direction label.
// - 039-039 envelope: direction indicator.
// - 040-040 envelope: envelope label.
//


// Positioning parameters.
#define SEQ_TRIG_POS_X 45
#define SEQ_TRIG_POS_Y 50
#define SEQ_TRIG_DIST 20
#define SEQ_ENV_POS_X 10
#define SEQ_ENV_POS_Y 10
#define SEQ_ENV_DIST  34

size_t obj_counter = 0;

typedef struct SeqSprite {
    u8 id;
    int x;
    int y;
    size_t base_tile;
    u16 obj_attr_0;
    u16 obj_attr_1;
    u16 obj_attr_2;
} SeqSprite;

int trig_selection_loc = 1;

SeqSprite seq_sprites[41] = {0};

void
init_sequencer_sprites(void) {
    // Sprite note names.
    size_t sprite_id = load_packed_sprite_data(&sprite_note_names, 2, 73);
    for (size_t i = 0; i < 16; ++i) {
        int x = SEQ_TRIG_POS_X + i * SEQ_TRIG_DIST;
        int y = SEQ_TRIG_POS_Y;
        int base_tile = sprites[sprite_id].tile_start;
        if (i >= 8) {
            y += 32;
            x -= 8 * SEQ_TRIG_DIST;
        }
        seq_sprites[i].x = x;
        seq_sprites[i].y = y;

        seq_sprites[i].id = obj_counter++;
        seq_sprites[i].base_tile = base_tile;
        seq_sprites[i].obj_attr_0 = OBJ_SHAPE_WIDE | OBJ_HIDDEN | OBJ_Y_COORD(y);
        seq_sprites[i].obj_attr_1 = OBJ_SIZE_SMALL | OBJ_X_COORD(x);
        seq_sprites[i].obj_attr_2 = base_tile;
    }

    // Trigger boxes.
    sprite_id = load_packed_sprite_data(&sprite_trigger_button, 8, 1);
    for (size_t i = 0; i < 16; ++i) {
        int x = SEQ_TRIG_POS_X + i * SEQ_TRIG_DIST;
        int y = SEQ_TRIG_POS_Y;
        int base_tile = sprites[sprite_id].tile_start;
        if (i >= 8) {
            y += 32;
            x -= 8 * SEQ_TRIG_DIST;
        }
        seq_sprites[i + 16].id = obj_counter++;
        seq_sprites[i + 16].base_tile = base_tile;
        seq_sprites[i + 16].obj_attr_0 = OBJ_SHAPE_TALL | OBJ_Y_COORD(y);
        seq_sprites[i + 16].obj_attr_1 = OBJ_SIZE_BIG | OBJ_X_COORD(x);
        seq_sprites[i + 16].obj_attr_2 = base_tile;
    }

    sprite_id = load_packed_sprite_data(&sprite_trigger_active_indicator, 1, 1);
    {
        int x = SEQ_TRIG_POS_X;
        int y = SEQ_TRIG_POS_Y + 15;
        int base_tile = sprites[sprite_id].tile_start;
        seq_sprites[32].id = obj_counter++;
        seq_sprites[32].base_tile = base_tile;
        seq_sprites[32].obj_attr_0 = OBJ_SHAPE_SQUARE | OBJ_Y_COORD(y);
        seq_sprites[32].obj_attr_1 = OBJ_SIZE_SMALL | OBJ_X_COORD(x);
        seq_sprites[32].obj_attr_2 = base_tile | OBJ_PAL_BANK(1);
    }

    sprite_id = load_packed_sprite_data(&sprite_trigger_selection, 16, 1);
    {
        int x = SEQ_TRIG_POS_X - 1 + trig_selection_loc * SEQ_TRIG_DIST;
        int y = SEQ_TRIG_POS_Y - 2;
        int base_tile = sprites[sprite_id].tile_start;
        if (trig_selection_loc >= 8) {
            y += 32;
            x -= 8 * SEQ_TRIG_DIST;
        }
        seq_sprites[33].id = obj_counter++;
        seq_sprites[33].base_tile = base_tile;
        seq_sprites[33].obj_attr_0 = OBJ_SHAPE_SQUARE | OBJ_Y_COORD(y);
        seq_sprites[33].obj_attr_1 = OBJ_SIZE_BIG | OBJ_X_COORD(x);
        seq_sprites[33].obj_attr_2 = base_tile | OBJ_PAL_BANK(2);
    }

    sprite_id = load_packed_sprite_data(&sprite_env_label_volume, 4, 1);
    {
        int x = SEQ_ENV_POS_X;
        int y = SEQ_ENV_POS_Y;
        int base_tile = sprites[sprite_id].tile_start;
        seq_sprites[34].id = obj_counter++;
        seq_sprites[34].base_tile = base_tile;
        seq_sprites[34].obj_attr_0 = OBJ_SHAPE_WIDE | OBJ_Y_COORD(y);
        seq_sprites[34].obj_attr_1 = OBJ_SIZE_MID | OBJ_X_COORD(x);
        seq_sprites[34].obj_attr_2 = base_tile | OBJ_PAL_BANK(2);
    }

    sprite_id = load_packed_sprite_data(&sprite_env_volume, 4, 16);
    {
        int x = SEQ_ENV_POS_X;
        int y = SEQ_ENV_POS_Y + 8;
        int base_tile = sprites[sprite_id].tile_start;
        seq_sprites[35].id = obj_counter++;
        seq_sprites[35].base_tile = base_tile;
        seq_sprites[35].obj_attr_0 = OBJ_SHAPE_WIDE | OBJ_Y_COORD(y);
        seq_sprites[35].obj_attr_1 = OBJ_SIZE_MID | OBJ_X_COORD(x);
        seq_sprites[35].obj_attr_2 = base_tile | OBJ_PAL_BANK(2);
    }

    sprite_id = load_packed_sprite_data(&sprite_env_label_time, 4, 1);
    {
        int x = SEQ_ENV_POS_X + SEQ_ENV_DIST;
        int y = SEQ_ENV_POS_Y;
        int base_tile = sprites[sprite_id].tile_start;
        seq_sprites[36].id = obj_counter++;
        seq_sprites[36].base_tile = base_tile;
        seq_sprites[36].obj_attr_0 = OBJ_SHAPE_WIDE | OBJ_Y_COORD(y);
        seq_sprites[36].obj_attr_1 = OBJ_SIZE_MID | OBJ_X_COORD(x);
        seq_sprites[36].obj_attr_2 = base_tile | OBJ_PAL_BANK(2);
    }

    sprite_id = load_packed_sprite_data(&sprite_env_time, 4, 8);
    {
        int x = SEQ_ENV_POS_X + SEQ_ENV_DIST;
        int y = SEQ_ENV_POS_Y + 8;
        int base_tile = sprites[sprite_id].tile_start;
        seq_sprites[37].id = obj_counter++;
        seq_sprites[37].base_tile = base_tile;
        seq_sprites[37].obj_attr_0 = OBJ_SHAPE_WIDE | OBJ_Y_COORD(y);
        seq_sprites[37].obj_attr_1 = OBJ_SIZE_MID | OBJ_X_COORD(x);
        seq_sprites[37].obj_attr_2 = base_tile | OBJ_PAL_BANK(2);
    }

    sprite_id = load_packed_sprite_data(&sprite_env_label_direction, 4, 1);
    {
        int x = SEQ_ENV_POS_X + SEQ_ENV_DIST * 2;
        int y = SEQ_ENV_POS_Y;
        int base_tile = sprites[sprite_id].tile_start;
        seq_sprites[38].id = obj_counter++;
        seq_sprites[38].base_tile = base_tile;
        seq_sprites[38].obj_attr_0 = OBJ_SHAPE_WIDE | OBJ_Y_COORD(y);
        seq_sprites[38].obj_attr_1 = OBJ_SIZE_MID | OBJ_X_COORD(x);
        seq_sprites[38].obj_attr_2 = base_tile | OBJ_PAL_BANK(2);
    }

    sprite_id = load_packed_sprite_data(&sprite_env_sweep_direction, 4, 2);
    {
        int x = SEQ_ENV_POS_X + SEQ_ENV_DIST * 2;
        int y = SEQ_ENV_POS_Y + 8;
        int base_tile = sprites[sprite_id].tile_start;
        seq_sprites[39].id = obj_counter++;
        seq_sprites[39].base_tile = base_tile;
        seq_sprites[39].obj_attr_0 = OBJ_SHAPE_WIDE | OBJ_Y_COORD(y);
        seq_sprites[39].obj_attr_1 = OBJ_SIZE_MID | OBJ_X_COORD(x);
        seq_sprites[39].obj_attr_2 = base_tile | OBJ_PAL_BANK(2);
    }

    sprite_id = load_packed_sprite_data(&sprite_env_label_env, 4, 1);
    {
        int x = SEQ_ENV_POS_X + SEQ_ENV_DIST;
        int y = SEQ_ENV_POS_Y - 8;
        int base_tile = sprites[sprite_id].tile_start;
        seq_sprites[40].id = obj_counter++;
        seq_sprites[40].base_tile = base_tile;
        seq_sprites[40].obj_attr_0 = OBJ_SHAPE_WIDE | OBJ_Y_COORD(y);
        seq_sprites[40].obj_attr_1 = OBJ_SIZE_MID | OBJ_X_COORD(x);
        seq_sprites[40].obj_attr_2 = base_tile | OBJ_PAL_BANK(2);
    }
}

void
update_sequencer_sprites(void) {
    // 000-015: Step note names.
    for (size_t i = 0; i < 16; ++i) {
        // Each note name is made of 2 8x8 tiles (16x8).
        size_t base_tile = sequence_synth[i].note * 2;

        // TODO: Show the note name if is within the duration, hide when trigger
        // is off or duration of previous note was cut short. If not triggered
        // but note name appears, needs to be on a different palette bank.
        if (!sequence_synth[i].trigger) {
            seq_sprites[i].obj_attr_0 |= OBJ_HIDDEN;
        } else {
            seq_sprites[i].obj_attr_0 &= ~OBJ_HIDDEN;
        }

        seq_sprites[i].obj_attr_2 = base_tile;
    }

    // 33: Sequence indicator.
    {
        int x = SEQ_TRIG_POS_X + step_counter * SEQ_TRIG_DIST + 3;
        int y = SEQ_TRIG_POS_Y + 15;
        if (step_counter >= 8) {
            y += 32;
            x -= 8 * SEQ_TRIG_DIST;
        }
        seq_sprites[32].obj_attr_0 = OBJ_SHAPE_SQUARE | OBJ_Y_COORD(y); // TODO: Mask and update instead.
        seq_sprites[32].obj_attr_1 = OBJ_SIZE_SMALL | OBJ_X_COORD(x);   // TODO: Mask and update instead.
    }

    // 34: Trigger selection.
    {
        int x = SEQ_TRIG_POS_X - 1 + trig_selection_loc * SEQ_TRIG_DIST;
        int y = SEQ_TRIG_POS_Y - 2;
        if (trig_selection_loc >= 8) {
            y += 32;
            x -= 8 * SEQ_TRIG_DIST;
        }
        // TODO: Mask and update instead.
        seq_sprites[33].obj_attr_0 = OBJ_SHAPE_SQUARE | OBJ_Y_COORD(y);
        seq_sprites[33].obj_attr_1 = OBJ_SIZE_BIG | OBJ_X_COORD(x);
    }

    // 36: Envelope initial volume
    {
        size_t tile_diff =  sequence_synth[trig_selection_loc].env_volume * 4;
        size_t base_tile = seq_sprites[35].base_tile;
        size_t tile = base_tile + tile_diff;
        seq_sprites[35].obj_attr_2 = tile | OBJ_PAL_BANK(2);
    }

    // 38: Envelope initial volume
    {
        size_t tile_diff =  sequence_synth[trig_selection_loc].env_time * 4;
        size_t base_tile = seq_sprites[37].base_tile;
        size_t tile = base_tile + tile_diff;
        seq_sprites[37].obj_attr_2 = tile | OBJ_PAL_BANK(2);
    }

    // 40: Envelope initial volume
    {
        size_t tile_diff =  sequence_synth[trig_selection_loc].env_direction * 4;
        size_t base_tile = seq_sprites[39].base_tile;
        size_t tile = base_tile + tile_diff;
        seq_sprites[39].obj_attr_2 = tile | OBJ_PAL_BANK(2);
    }
}

void
handle_sequencer_input(void) {
    if (key_pressed(KEY_LEFT)) {
        if (trig_selection_loc == 0) {
            trig_selection_loc = 15;
        } else {
            trig_selection_loc = CLAMP(trig_selection_loc - 1, 0, 15);
        }
    }
    if (key_pressed(KEY_RIGHT)) {
        if (trig_selection_loc == 15) {
            trig_selection_loc = 0;
        } else {
            trig_selection_loc = CLAMP(trig_selection_loc + 1, 0, 15);
        }
    }
    if (key_pressed(KEY_UP) || key_pressed(KEY_DOWN)) {
        trig_selection_loc = (trig_selection_loc + 8) % 16;
    }
    if (key_pressed(KEY_B)) {
        sequence_synth[trig_selection_loc].trigger ^= 1;
    }
    if (key_pressed(KEY_L)) {
        sequence_synth[trig_selection_loc].note = CLAMP(sequence_synth[trig_selection_loc].note - 1, NOTE_C_2, NOTE_C_8);
    }
    if (key_pressed(KEY_R)) {
        sequence_synth[trig_selection_loc].note = CLAMP(sequence_synth[trig_selection_loc].note + 1, NOTE_C_2, NOTE_C_8);
    }

    if (key_pressed(KEY_START)) {
        step_counter = 0;
        set_time(bpm);
    }
    if (key_pressed(KEY_SELECT)) {
        TIMER_CTRL_0 ^= TIMER_CTRL_ENABLE;
    }
}

void
render_sequencer_sprites(void) {
    size_t len = sizeof(seq_sprites) / sizeof(SeqSprite);
    for (size_t i = 0; i < len; ++i) {
        size_t id = seq_sprites[i].id;
        OBJ_ATTR_0(id) = seq_sprites[i].obj_attr_0;
        OBJ_ATTR_1(id) = seq_sprites[i].obj_attr_1;
        OBJ_ATTR_2(id) = seq_sprites[i].obj_attr_2;
    }
}