This interactive bar chart displays state-level firearm purchase background check data from the NICS (National Instant Criminal Background Check System) dataset. Animated via D3.js `transition`, the visualization compares total background checks across U.S. states and U.S. territories, with each bar stacked by firearm category (handgun, long gun, other, multiple). A legend hover effect dims non-hovered categories via `.attr('opacity', ...)`. Users can select a year, filter to show only the top 10 or 25 states, sort the bars by value or alphabetically, control the animation’s transition speed with a slider, and play an automatic year progression animation.