eco2d/code/modules/source/system_onfoot.c

void MoveWalk(ecs_iter_t *it) {
    Position *p = ecs_column(it, Position, 1);
    Velocity *v = ecs_column(it, Velocity, 2);
    
    for (int i = 0; i < it->count; i++) {
        world_block_lookup lookup = world_block_from_realpos(p[i].x, p[i].y);
        float drag = blocks_get_drag(lookup.block_id);
        v[i].x = zpl_lerp(v[i].x, 0.0f, PHY_WALK_DRAG*drag);
        v[i].y = zpl_lerp(v[i].y, 0.0f, PHY_WALK_DRAG*drag);
    }
}

#define PLR_MOVE_SPEED 50.0
#define PLR_MOVE_SPEED_MULT 4.0

void MovementImpulse(ecs_iter_t *it) {
    Input *in = ecs_column(it, Input, 1);
    Velocity *v = ecs_column(it, Velocity, 2);
    Position *p = ecs_term(it, Position, 3);
    
    for (int i = 0; i < it->count; i++) {
        world_block_lookup lookup = world_block_from_realpos(p[i].x, p[i].y);
        float drag = blocks_get_drag(lookup.block_id);
        double speed = PLR_MOVE_SPEED * (in[i].sprint ? PLR_MOVE_SPEED_MULT : 1.0);
        if (zpl_abs(v[i].x) < speed && in[i].x)
            v[i].x += in[i].x*speed*drag;
        if (zpl_abs(v[i].y) < speed && in[i].y)
            v[i].y += in[i].y*speed*drag;
    }
}