###### Abstract
In this study, we selected the Bollinger Bands trading strategy over others since Bollinger Bands provides a unique advantage by dynamically adapting to market volatility, offering a robust framework for identifying potential price reversals [29; 30]. Their flexibility and proven effectiveness make them a superior choice compared to static trading rules, enhancing adaptability to evolving market conditions and even optimizing trading opportunities [31; 32]. However, exploration of the Bollinger Bands trading strategy (BBTS) remains limited. Bitcoin and Ethereum (hereinafter referred to as ETH) are well-known blockchain-based cryptocurrencies [33; 34; 35; 36] that have received immense attention worldwide [37; 38; 39; 40; 3]. As such, this study aims to examine the efficacy of the Bollinger Bands Trading Strategy (BBTS) in the Bitcoin and Ethereum markets. Specific research objectives include evaluating BBTS's performance in different market conditions over the data period (i.e., from 2015-2022; eight-year data period), analyzing its performance, and assessing its potential as a reliable trading tool for these cryptocurrencies [26; 41]. The study seeks to contribute extensive insights into the BBTS application, enhancing transparency and understanding of its impact on cryptocurrency trading strategies. Consequently, this study uses Bitcoin and Ethereum spots, two of the most popular cryptocurrencies as our examined objectives to study whether investors using the BBTS would profit from trading these two spots. In addition, cryptocurrency prices, including those of Bitcoin and Ethereum, known for volatility [42; 43], create a unique landscape for potential gains [44]. Embracing the fluctuations, they are not setbacks but opportunities for significant rebounds [45]. The relevant research shows that these cryptocurrencies have the resilience to bounce back, making the dynamic nature of the market a compelling space for investors seeking substantial returns [46; 47]. As such, market participants may seize the moment, ride the waves, and let the volatility pave the way to financial opportunities. This study aims to explore whether investors would profit from BB round-turn trading (hereafter referred to as trading) in these two spots (i.e., Bitcoin and ETH spots). Following BBTS, investors are suggested to buy (sell) financial instruments (i.e., stocks and bonds) as oversold (overbought) signals emitted by the BBTS (i.e., penetrating lower (upper) Bollinger Bands) would be regarded as buying (selling) signals. As such, based on contrarian strategies implied by the BBTS as mentioned above, round-turn Bollinger Bands (BB) trading is defined as buying a cryptocurrency spot when a buy signal is issued (i.e., penetrating lower Bollinger Band) and after selling the cryptocurrency spot when an overbought signal is issued (i.e., penetrating upper Bollinger Band). We also further explore whether using our novel research design (i.e., utilizing the insights provided by a heatmap matrix) would result in greater returns across multiple outcomes in comparison to the conventional research design (i.e., searching for one of the trading rules that would have better performance than other trading rules among limited outcomes). This study can contribute to the existing literature in several ways. First, we investigate whether market participants would profit from trading these two most popular spots (i.e., Bitcoin and Ethereum spots) via the BBTS, which is understudied in the existing literature. Second, given that either spot prices or futures prices are likely to rebound after price overreactions, we can conclude that trading these two spots would generate profits, even substantial profits, which have rarely been reported in relevant studies. Third, we assert that using our new design (i.e., the wisdom of a heatmap matrix) would yield higher returns in some areas, all of which are higher than the highest return obtained using the conventional design in this study.