onst visibleStartMs = Math.max(guideStartMs, blockStartMs);
            const visibleEndMs = Math.min(guideEndMs, blockEndMs);
            
            const startOffset = (visibleStartMs - guideStartMs) / (1000 * 60); // minutes from guide start
            const endOffset = (visibleEndMs - guideStartMs) / (1000 * 60); // minutes from guide start
            const duration = endOffset - startOffset; // duration in minutes within the guide range
            
            // Calculate as percentages of the av