:root{--color-primary: #6c5ce7;--color-primary-hover: #5b4bd6;--color-primary-soft: #efecfe;--color-accent: #00c2a8;--color-accent-soft: #e0f9f5;--color-warn: #f5a623;--color-danger: #e5484d;--color-success: #2fb673;--color-bg: #f7f7fb;--color-surface: #ffffff;--color-surface-alt: #f1f1f8;--color-border: #e6e6f0;--color-text: #1c1c28;--color-text-muted: #6b6b80;--color-text-inverse: #ffffff;--shadow-sm: 0 1px 3px rgba(28, 28, 40, .06);--shadow-md: 0 6px 20px rgba(28, 28, 40, .08);--shadow-lg: 0 12px 32px rgba(28, 28, 40, .12);--sidebar-width: 264px;--sidebar-width-collapsed: 76px;--bottom-nav-height: 64px;--topbar-height: 64px;--radius-sm: 8px;--radius-md: 14px;--radius-lg: 20px;--radius-pill: 999px;--transition-fast: .15s ease;--transition-base: .22s ease;color-scheme:light}:root[data-theme=dark]{--color-primary: #8b7dfb;--color-primary-hover: #a094fc;--color-primary-soft: #2a2540;--color-accent: #35e4c6;--color-accent-soft: #123632;--color-bg: #14141c;--color-surface: #1c1c28;--color-surface-alt: #23232f;--color-border: #2e2e3d;--color-text: #f2f2f7;--color-text-muted: #a3a3b8;--color-text-inverse: #14141c;--shadow-sm: 0 1px 3px rgba(0, 0, 0, .3);--shadow-md: 0 6px 20px rgba(0, 0, 0, .35);--shadow-lg: 0 12px 32px rgba(0, 0, 0, .45);color-scheme:dark}*{box-sizing:border-box}html,body{height:100%}body{margin:0;font-family:Inter,-apple-system,BlinkMacSystemFont,Segoe UI,Roboto,sans-serif;background:var(--color-bg);color:var(--color-text);transition:background var(--transition-base),color var(--transition-base);-webkit-font-smoothing:antialiased}h1,h2,h3,h4,p{margin:0}button,input,select,textarea{font-family:inherit}a{color:inherit;text-decoration:none}:focus-visible{outline:2px solid var(--color-primary);outline-offset:2px}.card{background:var(--color-surface);border:1px solid var(--color-border);border-radius:var(--radius-lg);padding:22px 24px;box-shadow:var(--shadow-sm)}.card__eyebrow{display:block;font-size:.75rem;font-weight:700;text-transform:uppercase;letter-spacing:.04em;color:var(--color-text-muted);margin-bottom:10px}.card__big-number{font-size:1.7rem;font-weight:800;margin-bottom:14px}.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;padding:11px 20px;border-radius:var(--radius-pill);font-weight:700;font-size:.88rem;border:none;cursor:pointer;transition:transform var(--transition-fast),background var(--transition-fast),box-shadow var(--transition-fast)}.btn:disabled{opacity:.5;cursor:not-allowed}.btn--primary{background:linear-gradient(135deg,var(--color-primary),var(--color-primary-hover));color:var(--color-text-inverse);box-shadow:var(--shadow-sm)}.btn--primary:hover:not(:disabled){transform:translateY(-1px);box-shadow:var(--shadow-md)}.btn--ghost{background:var(--color-surface-alt);color:var(--color-text)}.btn--ghost:hover:not(:disabled){background:var(--color-border)}.btn--block{width:100%}.exercise-prompt{font-size:1.05rem;font-weight:700;margin-bottom:18px}.exercise-options{display:flex;flex-direction:column;gap:10px}.exercise-option{display:flex;align-items:center;gap:10px;width:100%;padding:14px 16px;border-radius:var(--radius-md);border:2px solid var(--color-border);background:var(--color-surface);color:var(--color-text);font-size:.92rem;font-weight:600;text-align:left;cursor:pointer;transition:border-color var(--transition-fast),background var(--transition-fast),transform var(--transition-fast)}.exercise-option:hover:not(:disabled){border-color:var(--color-primary);transform:translateY(-1px)}.exercise-option:disabled{cursor:default}.exercise-option--selected{border-color:var(--color-primary);background:var(--color-primary-soft)}.exercise-option--correct{border-color:var(--color-success);background:color-mix(in srgb,var(--color-success) 14%,var(--color-surface))}.exercise-option--incorrect{border-color:var(--color-danger);background:color-mix(in srgb,var(--color-danger) 14%,var(--color-surface))}.exercise-feedback{display:flex;align-items:flex-start;gap:10px;padding:14px 16px;border-radius:var(--radius-md);font-size:.88rem;margin-top:18px}.exercise-feedback--correct{background:color-mix(in srgb,var(--color-success) 14%,transparent);color:var(--color-success)}.exercise-feedback--incorrect{background:color-mix(in srgb,var(--color-danger) 14%,transparent);color:var(--color-danger)}.exercise-feedback__body{display:flex;flex-direction:column;gap:4px}.exercise-feedback__body strong{font-size:.92rem}.exercise-feedback__body span{color:var(--color-text-muted);font-weight:500}.visually-hidden{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap}@media(prefers-reduced-motion:reduce){*,*:before,*:after{animation-duration:.01ms!important;animation-iteration-count:1!important;transition-duration:.01ms!important;scroll-behavior:auto!important}}html,body{max-width:100%;overflow-x:hidden}