Players.cpp

//@abi action
void update(account_name account, uint64_t level, int64_t healthPoints, int64_t energyPoints) {
    require_auth(account);

    playerIndex players(_self, _self);

    auto iterator = players.find(account);
    eosio_assert(iterator != players.end(), "Address for account not found");

    /**
     * We add the new player in the table
     * The first argument is the payer of the storage which will store the data
    */
    players.modify(iterator, account, [&](auto& player) {
        player.level = level;

        if ((player.health_points - healthPoints) < 0) {
            player.health_points = 0;
        } else {
            player.health_points -= healthPoints;
        }

        if ((player.energy_points - energyPoints) < 0) {
            player.energy_points = 0;
        } else {
            player.energy_points -= energyPoints;
        }
    });
}

You forgot updating the comment.

/**
 * Find and update the player in the table
 * The first argument is the current player, the second is the payer of the storage which will store the data
 */