21天突破高频词汇 vs PhysicsBench

把难词，变成旧朋友。 《21天突破高频词汇》把 2,121 个核心词汇整理成 21 天学习计划。每天一组，先看全貌，再用词卡逐个学习，最后通过复习把掌握情况变成看得见的进度。 【每天都有清晰目标】 21 天分组呈现，不必面对一整本单词书。进入当天章节，一屏浏览全部单词，快速建立整体印象。 【词卡信息完整】 每张词卡包含单词、音标、词性、中文释义和例句。左右滑动即可切换，保持连续学习节奏。 【两种复习方式】 可以按天复习，也可以从全部未掌握单词中随机抽查。先回想答案，再翻开词卡核对，减少“看着眼熟、合上就忘”的错觉。 【三次记住，进度清楚】 同一单词累计标记“已记住”1 次后，会进入已掌握状态并自动移出复习词池；选择“未记住”则重新计数。整体进度页会显示已掌握、学习中和尚未开始的数量。 【离线、轻量、无负担】 无需注册账号，没有广告或 App 内购买。词库和学习进度均保存在设备本地，没有网络时也能学习。 适合希望用固定周期集中积累英语核心词汇、建立每日学习节奏的备考者和英语学习者。 21 天不是记忆的终点，而是一套更容易开始、也更容易坚持的学习安排。

Solve real physics, not fake wiring puzzles. PhysicsBench simulates actual circuits, light paths and torque — then shows you the formula behind your solution. Wire a battery, close a switch, watch current flow and a bulb light up. Bounce a beam off mirrors into the target. Balance a lever with the right weights. Every level ends with a Principle Card: the law, the formula, and your level's real numbers substituted in. MAIN FEATURES • 108 levels across seven subjects: Circuits, Optics, Mechanics, Dynamics, Electromagnetism, Heat & Fluids, Waves & Sound • Three difficulties per subject: Intro, Core, Brainer • True simulation — nodal analysis for DC circuits with diodes and capacitors, ray tracing for light, torque balance, and closed-form models for motion, induction, heat and sound • Principle Card after every solve, with your own values • Daily experiment with streaks • Courses by topic, a review queue for levels you needed hints on, and a mastery radar • Unlimited hints, never a consumable • Import and play levels friends share as a code or .physlab file • Home-screen widget, Apple Pencil notes and bench recording • Works fully offline. No ads, no accounts, no tracking PRO — ONE-TIME PURCHASE • All 108 levels, including every Brainer level • Full step-by-step derivation on every Principle Card • Frame-by-frame replay with velocity and force arrows, and a draggable RC charging curve • Free Bench lab: sliders for every model, plus building, naming and saving experiments • Level editor that proves your puzzle is solvable before you share it • Full probe panel: per-branch voltage, current and power; every beam path; torque breakdown • Four extra themes and three alternate app icons • Future local Pro levels in this app ANSWER REPORTS — OPTIONAL Stuck? Unlock the worked answer for a difficulty with a separate one-time purchase: the solved bench, every move with its reason and the principle worked through. Not included in Pro; hints stay free. PRIVACY Everything runs on your device. Progress syncs through your own private iCloud. No account, no analytics SDK, no data sent to us. NOTE Levels use teaching-simplified models (ideal wires, batteries with internal resistance, single-colour rays). The in-app "About the model" page lists every assumption. Support · Privacy Policy · Terms of Use are in Settings.