demo/snake/snake.c

/*
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS HEADER.
 * Copyright 2023 Mike Becker. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *   1. Redistributions of source code must retain the above copyright
 *      notice, this list of conditions and the following disclaimer.
 *
 *   2. Redistributions in binary form must reproduce the above copyright
 *      notice, this list of conditions and the following disclaimer in the
 *      documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 * POSSIBILITY OF SUCH DAMAGE.
 */

#include <ascension/core.h>
#include <ascension/ui.h>
#include <ascension/sprite.h>
#include <ascension/2d.h>
#include <ascension/shader.h>
#include <ascension/util.h>

#include <cx/printf.h>
#include <cx/linked_list.h>

#define TEXTURE_2D_COUNT 3
static AscTexture tex2d[TEXTURE_2D_COUNT];
#define TEXTURE_PLAYER &tex2d[0]
#define TEXTURE_PLAYER_COLOR_MAP &tex2d[1]
#define TEXTURE_BACKDROP &tex2d[2]

#define SHADER_ID_PLAYER 1

#define BACKDROP_SCENE asc_window_scene(0)
#define MAIN_SCENE asc_window_scene(1)
#define HUD_WIDTH 400

enum MoveDirection {
    MOVE_UP,
    MOVE_LEFT,
    MOVE_DOWN,
    MOVE_RIGHT
};

static asc_transform rotations[4];
static asc_vec2i directions[4];

typedef struct {
    AscSceneNode *node;
    asc_color color;
    enum MoveDirection direction;
    enum MoveDirection target_direction;
    /**
     * The number of tiles this player can look.
     */
    float view_distance;
    /**
     * The speed in tiles per second.
     */
    float speed;
    /**
     * A linked list of vec2u elements describing the current trace.
     */
    CxList *trace;
    /**
     * The new position of the player when @c reset_position is @c true.
     */
    asc_vec2u new_position;
    unsigned health;
    bool alive;
    bool reset_position;
    uint8_t number;
} Player;

#define GAME_FIELD_SIZE 32
#define GAME_FIELD_TILE_SIZE 32

/** The bit in the tile data indicating if the tile exists. */
#define GAME_FIELD_TILE_EXISTS_FLAG  0x80
/** The bits in the tile data that identify the owner. */
#define GAME_FIELD_TILE_OWNER_MASK   0x0F

typedef struct {
    AscSceneNode *nodes[GAME_FIELD_SIZE][GAME_FIELD_SIZE];
    uint8_t tile_data[GAME_FIELD_SIZE][GAME_FIELD_SIZE];
} GameField;


#define GAME_STATE_MENU 0
#define GAME_STATE_PLAYING 1
#define GAME_STATE_GAME_OVER 2

typedef struct {
    int state;
    GameField *field;
    Player *players[4];
} GameState;

GameState game = {0};

static void globals_init(void) {
    asc_transform_identity(rotations[MOVE_UP]);
    asc_transform_roll(rotations[MOVE_LEFT], asc_rad(-90));
    asc_transform_roll(rotations[MOVE_RIGHT], asc_rad(90));
    asc_transform_roll(rotations[MOVE_DOWN], asc_rad(180));
    directions[MOVE_UP] = ASC_VEC2I(0, -1);
    directions[MOVE_LEFT] = ASC_VEC2I(-1, 0);
    directions[MOVE_DOWN] = ASC_VEC2I(0, 1);
    directions[MOVE_RIGHT] = ASC_VEC2I(1, 0);
}

static void textures_destroy(void) {
    asc_texture_destroy(tex2d, TEXTURE_2D_COUNT);
}

static void textures_init(void) {
    // don't use interpolation for pixel art
    asc_texture_init(tex2d, 2, ASC_TEXTURE_2D,
        ASC_TEXTURE_MIN_FILTER_NEAREST, ASC_TEXTURE_MAG_FILTER_NEAREST);
    asc_texture_from_file(TEXTURE_PLAYER, "player.png");
    asc_texture_from_file(TEXTURE_PLAYER_COLOR_MAP, "player-color-map.png");
    // interpolate larger, not pixelated, textures
    asc_texture_init(tex2d+2, 1, ASC_TEXTURE_2D,
        ASC_TEXTURE_MIN_FILTER_LINEAR, ASC_TEXTURE_MAG_FILTER_LINEAR);
    asc_texture_from_file(TEXTURE_BACKDROP, "backdrop.png");
    asc_gl_context_add_cleanup_func(asc_active_glctx, textures_destroy);
}

static void backdrop_scale(AscBehavior *behavior) {
    // scale the backdrop to the size of the window
    if (!asc_active_window->resized) return;
    asc_ptr_cast(AscSprite, sprite, behavior->node);
    asc_vec2u window_size = asc_active_window->rect.size;
    asc_sprite_set_size(sprite, window_size);
}

static void main_scene_frame_scale(AscBehavior *behavior) {
    if (!asc_active_window->resized) return;
    asc_ptr_cast(AscRectangle, frame, behavior->node);
    asc_rectangle_set_bounds(frame, asc_scene_viewport(MAIN_SCENE));
}

static void backdrop_create(void) {
    const float scale = 1.f / asc_active_window->ui_scale;
    AscSceneNode *node = asc_sprite(
        .texture = TEXTURE_BACKDROP,
        .texture_scale_mode = ASC_TEXTURE_SCALE_REPEAT,
        .texture_scale_x = scale, .texture_scale_y = scale,
    );
    asc_behavior_add(node, .func = backdrop_scale);
    asc_scene_add_node(BACKDROP_SCENE, node);

    // also add a frame for the main scene
    // add this to the UI layer so that the border size does not scale
    AscSceneNode *frame = asc_rectangle(.thickness = 2, .color = ASC_RGBi(66, 142, 161));
    asc_behavior_add(frame, .func = main_scene_frame_scale);
    asc_ui_add_node(frame);
}

static void fps_counter_update(AscBehavior *behavior) {
    asc_ptr_cast(AscText, node, behavior->node);
    asc_text_printf(node,
        "%.2f FPS\n"
        "%llu draw calls\n"
        "%llu triangles\n"
        "%llu vertices",
        asc_context.frame_rate,
        asc_active_glctx->counters.draw_calls,
        asc_active_glctx->counters.triangles_rendered,
        asc_active_glctx->counters.vertices_rendered);
}

static void fps_counter_tie_to_corner(AscBehavior *behavior) {
    // TODO: this should be replaced with some sort of UI layout manager
    AscSceneNode *node = behavior->node;
    if (asc_test_flag(node->flags, ASC_SCENE_NODE_GRAPHICS_UPDATED) || asc_active_window->resized) {
        // TODO: this is visually wrong for one frame
        //       instead there should be alignment settings with which we can control if (0,0) is in top left or bottom left corner
        asc_scene_node_set_position2f(node, ASC_VEC2F(10,
                asc_active_window->rect.size.height - ((AscText*)node)->dimension.height - 10
        ));
    }
}

static AscSceneNode *fps_counter_create(void) {
    AscSceneNode *node = asc_text(
        .name = "FPS Counter",
        .color = ASC_RGB(1, 1, 1),
        .font = asc_font(ASC_FONT_REGULAR, 12),
    );
    asc_behavior_add(node, .func = fps_counter_update, .interval = asc_seconds(1));
    asc_behavior_add(node, fps_counter_tie_to_corner);
    asc_behavior_disable_all_while_hidden(node);
    asc_ui_add_node(node);
    return node;
}

static void game_over_text_keep_centered(AscBehavior *behavior) {
    if (!behavior->reactivated && !asc_active_window->resized) return;

    AscSceneNode *node = behavior->node;
    // center the "game over" text in the game field viewport
    const asc_rect main_scene_viewport = asc_scene_viewport(MAIN_SCENE);
    asc_scene_node_set_position2f(node, ASC_VEC2F(
        main_scene_viewport.pos.x + main_scene_viewport.size.x / 2.f,
        main_scene_viewport.pos.y + main_scene_viewport.size.y / 2.f - 36
    ));
}

static AscSceneNode *game_over_create_text(void) {
    AscSceneNode *node = asc_text(
        .name = "game_over_text",
        .text = "Game Over\nPress R to Restart",
        .color = ASC_RGB(1, 1, 1),
        .font = asc_font(ASC_FONT_REGULAR, 36),
        .alignment = ASC_TEXT_ALIGN_CENTER,
        .centered = true,
    );

    asc_scene_node_hide(node);
    asc_behavior_add(node, game_over_text_keep_centered, .disable_while_hidden = true);
    asc_ui_add_node(node);

    return node;
}

static bool game_field_tile_occupied(asc_vec2u coords) {
    unsigned x = coords.x, y = coords.y;
    return game.field->tile_data[x][y] & GAME_FIELD_TILE_OWNER_MASK;
}

static void game_field_tile_chown(asc_vec2u coords, Player *player) {
    unsigned x = coords.x, y = coords.y;
    asc_ptr_cast(AscRectangle, tile, game.field->nodes[x][y]);
    if (player == NULL) {
        asc_clear_flag(game.field->tile_data[x][y], GAME_FIELD_TILE_OWNER_MASK);
        tile->color = ASC_RGBi(16, 50, 160);
    } else {
        asc_set_flag_masked(game.field->tile_data[x][y], GAME_FIELD_TILE_OWNER_MASK, player->number);
        tile->color = player->color;
    }
}

static void game_field_create() {
    // TODO: create a more interesting map than just a basic grid
    AscSceneNode *node = asc_scene_node_empty();
    game.field = asc_scene_node_allocate_data(node, sizeof(GameField));
    for (unsigned x = 0; x < GAME_FIELD_SIZE; x++) {
        for (unsigned y = 0; y < GAME_FIELD_SIZE; y++) {
            AscSceneNode *tile = asc_rectangle(
                .x = x*GAME_FIELD_TILE_SIZE, .y = y*GAME_FIELD_TILE_SIZE, .filled = true, .thickness = 2,
                .width = GAME_FIELD_TILE_SIZE, .height = GAME_FIELD_TILE_SIZE,
                .color = ASC_RGBi(16, 50, 160),
                .border_color = ASC_RGBi(20, 84, 128),
            );

            game.field->tile_data[x][y] = GAME_FIELD_TILE_EXISTS_FLAG;
            game.field->nodes[x][y] = tile;

            asc_scene_node_add(node, tile);
        }
    }
    asc_scene_node_set_zindex(node, -2);
    asc_scene_add_node(MAIN_SCENE, node);
}

static asc_vec2u game_field_tile_at_position(asc_vec3f position) {
    return ASC_VEC2U((int)position.x / GAME_FIELD_TILE_SIZE, (int)position.y / GAME_FIELD_TILE_SIZE);
}

typedef struct {
    AscShaderProgram program;
    asc_uniform_loc map_albedo;
    asc_uniform_loc map_color;
    asc_uniform_loc color;
} PlayerShader;

static void player_shader_init(AscShaderProgram *p, CX_UNUSED int flags) {
    asc_shader_set_uniform_loc_by_name(p, PlayerShader, map_albedo);
    asc_shader_set_uniform_loc_by_name(p, PlayerShader, map_color);
    asc_shader_set_uniform_loc_by_name(p, PlayerShader, color);
}

static AscShaderProgram *player_shader_create(CX_UNUSED int unused) {
    return asc_shader_create((AscShaderCodes) {
        .vtx = {.source_file = "sprite_vtx.glsl"},
        .frag = {.source_file = "player.glsl",},
    }, sizeof(PlayerShader), player_shader_init, 0);
}

static void player_draw(const AscCamera *camera, const AscSceneNode *node) {
    asc_cptr_cast(AscSprite, sprite, node);
    const Player *player = node->user_data;

    // TODO: we shall finally add the shader information to the node
    const AscShaderProgram *s = asc_shader_lookup(
        SHADER_ID_PLAYER, player_shader_create, 0
    );
    if (asc_shader_use(s, camera)) return;
    asc_cptr_cast(PlayerShader, shader, s);

    asc_shader_upload_model_matrix(s, node);

    // Bind texture
    asc_texture_bind(TEXTURE_PLAYER, shader->map_albedo, 0);
    asc_texture_bind(TEXTURE_PLAYER_COLOR_MAP, shader->map_color, 1);
    asc_shader_upload_color(shader->color, player->color);
    asc_mesh_draw_triangle_strip(&sprite->mesh);
}

static void player_position(Player *pl, unsigned x, unsigned y) {
    pl->new_position.x = x;
    pl->new_position.y = y;
    pl->reset_position = true;
}

static void player_position_random(Player *pl) {
    // TODO: check if the spawn location is viable when there is more action on the board
    player_position(
        pl,
        4u + asc_util_rand(GAME_FIELD_SIZE - 8u),
        4u + asc_util_rand(GAME_FIELD_SIZE - 8u)
    );
}

static void player_main_behavior(AscBehavior *behavior) {
    AscSceneNode *node = behavior->node;
    Player *player = node->user_data;

    if (player->alive && player->health == 0) {
        player->alive = false;
        asc_scene_node_hide(node);
        // TODO: probably we don't want the entire trace to disappear instantly
        cxListClear(player->trace);
        // TODO: this should be controlled by another behavior that watches all players
        game.state = GAME_STATE_GAME_OVER;
    }

    // TODO: replace with respawn event
    if (!player->alive && player->health > 0) {
        player_position_random(player);
        player->alive = true;
        asc_scene_node_show(node);
    }
}

static void player_move(AscBehavior *behavior) {
    AscSceneNode *node = behavior->node;
    Player *player = node->user_data;

    const float ts = (float) GAME_FIELD_TILE_SIZE;

    // determine the current tile's coordinates
    const asc_vec2u old_tile = game_field_tile_at_position(node->position);

    // check if the position is set programmatically
    if (player->reset_position) {
        asc_scene_node_set_position2f(node,
            ASC_VEC2F(
                ts * (player->new_position.x + .5f),
                ts * (player->new_position.y + .5f)
            ));
        player->reset_position = false;
        return;
    }

    // normal movement
    const float speed = ts * player->speed * asc_context.frame_factor;
    const asc_vec2i dir = directions[player->direction];
    const asc_vec2f movement = asc_vec2f_scale(asc_vec2_itof(dir), speed);

    // check if we are supposed to change the direction
    if (player->direction == player->target_direction) {
        // move without changing the direction
        asc_scene_node_move2f(node, movement);
    } else {
        // determine axis
        // and check if we are about to cross the center
        // this relies on positive positions!
        bool rotate = false;
        if (movement.x == 0) {
            // vertical movement
            const float y_0 = floorf(node->position.y / ts);
            const float y_curr = node->position.y / ts - y_0;
            const float y_next = (node->position.y+movement.y) / ts - y_0;
            const bool side_curr = y_curr > 0.5f;
            const bool side_next = y_next > 0.5f;
            rotate = side_curr ^ side_next;
        } else {
            // horizontal movement
            const float x0 = floorf(node->position.x / ts);
            const float x_curr = node->position.x / ts - x0;
            const float x_next = (node->position.x+movement.x) / ts - x0;
            const bool side_curr = x_curr > 0.5f;
            const bool side_next = x_next > 0.5f;
            rotate = side_curr ^ side_next;
        }
        if (rotate) {
            // snap position to the center of the tile
            asc_scene_node_set_position2f(node,
            ASC_VEC2F(
                (.5f+floorf(node->position.x / ts)) * ts,
                (.5f+floorf(node->position.y / ts)) * ts
            ));
            player->direction = player->target_direction;
            asc_scene_node_set_rotation(node, rotations[player->direction]);
        } else {
            // changing the direction not permitted, yet, continue movement
            asc_scene_node_move2f(node, movement);
        }
    }

    // die when leaving the game field
    if (node->position.x < 0 || node->position.y < 0 ||
        node->position.x > GAME_FIELD_SIZE*ts ||
        node->position.y > GAME_FIELD_SIZE*ts) {
        // TODO: replace setting health to zero with a "kill" event
        player->health = 0;
        return;
    }

    // TODO: collision with other players

    // determine the new tile's coordinates
    const asc_vec2u new_tile = game_field_tile_at_position(node->position);

    // tile did not change - stop here
    if (asc_vec2u_eq(old_tile, new_tile)) return;

    // die when colliding with a player's trace
    if (game_field_tile_occupied(new_tile)) {
        // TODO: replace setting health to zero with a "kill" event
        player->health = 0;
        return;
    }

    // update own trace
    game_field_tile_chown(old_tile, player);
    cxListAdd(player->trace, &old_tile);
    if (cxListSize(player->trace) > 7) {
        // TODO: implement power-up which makes the trace longer
        cxListRemove(player->trace, 0);
    }
}

static void player_controls(AscBehavior *behavior) {
    Player *player = behavior->node->user_data;
    // TODO: different key bindings for different player number in hot seat mode
    if (asc_key_pressed(ASC_KEY(LEFT))) {
        if (player->direction != MOVE_RIGHT) {
            player->target_direction = MOVE_LEFT;
        }
    }
    if (asc_key_pressed(ASC_KEY(RIGHT))) {
        if (player->direction != MOVE_LEFT) {
            player->target_direction = MOVE_RIGHT;
        }
    }
    if (asc_key_pressed(ASC_KEY(UP))) {
        if (player->direction != MOVE_DOWN) {
            player->target_direction = MOVE_UP;
        }
    }
    if (asc_key_pressed(ASC_KEY(DOWN))) {
        if (player->direction != MOVE_UP) {
            player->target_direction = MOVE_DOWN;
        }
    }
}

static void player_destroy(CxAllocator *allocator, Player *player) {
    cxListFree(player->trace);
    cxFree(allocator, player);
}

static void player_trace_release_tile(asc_vec2u *coords) {
    game_field_tile_chown(*coords, NULL);
}

static Player *player_create(void) {
    AscSceneNode *node = asc_sprite(
        .name = "Player",
        .width = GAME_FIELD_TILE_SIZE,
        .height = GAME_FIELD_TILE_SIZE,
        .origin_x = GAME_FIELD_TILE_SIZE / 2,
        .origin_y = GAME_FIELD_TILE_SIZE / 2,
    );
    asc_scene_add_node(MAIN_SCENE, node);
    Player *player = asc_scene_node_allocate_data(node, sizeof(Player));
    player->node = node;
    player->view_distance = 7.f; // start with 7 tiles
    player->speed = 3.f; // start with 3 tiles/sec
    player->number = 1;
    player->health = 100;
    player->color = ASC_RGB(1, 0, 0);
    player->trace = cxLinkedListCreate(NULL, sizeof(asc_vec2u));
    cxSetDestructor(player->trace, player_trace_release_tile);
    node->draw_func = player_draw;
    node->user_data_free_func = (cx_destructor_func2)player_destroy;

    // add behaviors
    asc_behavior_add(node, player_main_behavior, .always_enabled = true);
    asc_behavior_add(node, player_controls);
    asc_behavior_add(node, player_move);
    asc_behavior_disable_all_while_hidden(node);

    return player;
}

static void main_scene_viewport_update(AscCamera *camera, asc_vec2u window_size) {
    // margins
    const unsigned margin = 16;

    // space for score, power-ups, etc.
    const unsigned left_area = (unsigned) (asc_active_window->ui_scale*HUD_WIDTH);

    // calculate how many pixels need to be removed from width and height
    const unsigned rw = 2*margin + left_area;
    const unsigned rh = 2*margin;

    // check if there is still a viewport left and chicken out when not
    if (window_size.width < rw || window_size.height < rh) {
        camera->viewport = ASC_RECT(0, 0, 0, 0);
        return;
    }
    window_size.width -= rw;
    window_size.height -= rh;

    // Compute scaling and offsets
    unsigned viewport_size, offset_x = 0, offset_y = 0;
    if (window_size.width > window_size.height) {
        // Wider window: letterbox (black bars on top/bottom)
        offset_x = (window_size.width - window_size.height) / 2;
        viewport_size = window_size.height;
    } else {
        // Taller window: pillarbox (black bars on sides)
        offset_y = (window_size.height - window_size.width) / 2;
        viewport_size = window_size.width;
    }
    offset_x += left_area + margin;
    offset_y += margin;

    // Set the viewport to the scaled and centered region
    camera->viewport = ASC_RECT(offset_x, offset_y, viewport_size, viewport_size);
}

static void main_scene_camera_update(AscCamera *camera) {
    // follow the player
    // TODO: for hot seat / split screen updates we need to attach custom data to the camera
    //       s.t. the camera knows which player to follow
    const Player *player = game.players[0];

    const AscSceneNode *player_node = player->node;
    const float view_distance = player->view_distance;
    const float cam_view_distance = (1+view_distance) * GAME_FIELD_TILE_SIZE;
    const float proj_size = 2 * cam_view_distance;

    // TODO: create camera API to avoid direct access to the matrices

    // update the projection matrix
    asc_mat4f_ortho_update_size(camera->projection, proj_size, proj_size);

    // update the view matrix
    asc_vec2f pos = asc_scene_node_get_position2f(player_node);
    pos.x = -pos.x + cam_view_distance;
    pos.y = -pos.y + cam_view_distance;
    asc_transform_translate2f(camera->view, pos);
}

int main(void) {
    asc_context_initialize();
    if (asc_has_error()) {
        SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR,
                "Fatal Error",asc_get_error(), NULL);
        return 1;
    }

    // initialize globals
    globals_init();

    // create the window
    asc_window_initialize(0, asc_gl_context_settings_default(4, 0));
    asc_window_set_title(0, "Snake");
    asc_window_set_size(0, asc_vec2_ftou(
        asc_vec2f_scale(ASC_VEC2F(600+HUD_WIDTH, 600), asc_ui_scale_auto())));
    asc_window_center(0);

    // load textures
    textures_init();

    // initialize backdrop scene
    AscCamera backdrop_camera;
    asc_camera_init(&backdrop_camera,
        .type = ASC_CAMERA_ORTHO,
        .viewport_update_func = asc_camera_ortho_update_size
    );
    asc_scene_init(BACKDROP_SCENE, "backdrop", &backdrop_camera);
    backdrop_create();

    // Initialize the main scene
    AscCamera main_camera;
    asc_camera_init(&main_camera,
        .type = ASC_CAMERA_ORTHO,
        .viewport_clear = true,
        .clear_color = ASC_RGBi(0, 32, 16),
        .viewport_update_func = main_scene_viewport_update,
        .update_func = main_scene_camera_update
    );
    asc_scene_init(MAIN_SCENE, "main", &main_camera);

    // create the fps counter
    AscSceneNode *fps_counter = fps_counter_create();
    asc_scene_node_hide(fps_counter);

    // create game over text
    AscSceneNode *text_game_over = game_over_create_text();

    // initialize the game state
    // TODO: add a main menu and start with the menu
    game.state = GAME_STATE_PLAYING;
    game.players[0] = player_create();
    game_field_create();

    // Main Loop
    do {
        // quit application on any error
        if (asc_has_error()) {
            SDL_ShowSimpleMessageBox(SDL_MESSAGEBOX_ERROR,
                    "Fatal Error", asc_get_error(),
                    asc_active_window->sdl);
            asc_clear_error();
            asc_context_quit();
        }

        // game states
        // TODO: move this into a behavior - probably add a state machine that enables/disables behaviors
        if (game.state == GAME_STATE_GAME_OVER) {
            asc_scene_node_show(text_game_over);
            if (asc_key_pressed(ASC_KEY(R))) {
                // TODO: instead of setting the health, send a "respawn" event to the behavior
                game.players[0]->health = 100;
                // TODO: re-load the "level"
                game.state = GAME_STATE_PLAYING;
                asc_scene_node_hide(text_game_over);
            }
        }

        // debug-key for clearing the shader registry
        if (asc_key_pressed(ASC_KEY(S))) {
            asc_shader_clear_registry();
        }

        // show/hide the FPS counter
        if (asc_key_pressed(ASC_KEY(F2))) {
            asc_scene_node_toggle_visibility(fps_counter);
        }

        // quit application on ESC key press
        if (asc_key_pressed(ASC_KEY(ESCAPE))) {
            asc_context_quit();
        }
    } while (asc_loop_next());

    // cleanup
    asc_context_destroy();
    return 0;
}