Explore the connections between clinical conditions, ion changes, and ECG patterns more clearly. - Ion & ECG: Expanded the adjustable parameters, including Na⁺ and H⁺ (pH), and clarified links to clinical conditions and differences from the reference. Improved consistency between action-potential calculations and ECG timing displays. - ECG & Conditions: Compare representative patterns with the normal reference in single-lead or 12-lead views, with clearer explanations of waveform features and mechanisms. Explore examples of a healthy child around age 5, fever-related sinus tachycardia, and higher-BMI body habitus. - Refined the medical consistency of the educational models, including pediatric waveforms, bundle-branch conduction, atrial fibrillation, and ST changes. Improved alignment between ECG traces and 3D activation and repolarization. Added representative P-wave flattening and PR prolongation at high K⁺, and ST depression in the left ventricular hypertrophy strain pattern. - ECG Mechanism: Made two-lead comparison easier to find and improved alignment between waveforms, 3D views, and playback position. Electrode placement now includes all 10 electrodes used for a standard 12-lead ECG, including the neutral RL electrode. - Improved text, buttons, and layouts throughout the app, including the iPhone feature list and navigation, iPad numerical displays, and Pro screen controls. Revised quiz presentation and explanations. This is an educational model, not a tool for diagnosis, treatment decisions, or patient-specific waveform prediction.