:root {
    --bg-color: #0A192F;
    --bg-gradient: linear-gradient(180deg, #112240 0%, #0A192F 100%);
    --primary-text: #CCD6F6;
    --secondary-text: #8892B0;
    --accent-color: #64FFDA;
    --accent-darker: #00C79E;
    --card-bg: #112240;
    --border-color: #233554;
    --correct-color: #28a745;
    --correct-glow: rgba(40, 167, 69, 0.6);
    --incorrect-color: #dc3545;
    --incorrect-glow: rgba(220, 53, 69, 0.6);
    --sign-bit-bg: rgba(220, 53, 69, 0.2);
    --exponent-bg: rgba(255, 193, 7, 0.2);
    --font-sans: 'Poppins', sans-serif;
    --font-mono: 'Roboto Mono', monospace;
}

/* --- KEYFRAME ANIMATIONS --- */
@keyframes fadeInUp {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}
@keyframes feedbackPop {
    0% { opacity: 0; transform: scale(0.9); }
    100% { opacity: 1; transform: scale(1); }
}
@keyframes scorePulse {
    0% { transform: scale(1); }
    50% { transform: scale(1.1); }
    100% { transform: scale(1); }
}
@keyframes shake {
  10%, 90% { transform: translate3d(-1px, 0, 0); }
  20%, 80% { transform: translate3d(2px, 0, 0); }
  30%, 50%, 70% { transform: translate3d(-4px, 0, 0); }
  40%, 60% { transform: translate3d(4px, 0, 0); }
}

* {
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}
body {
    font-family: var(--font-sans);
    background-color: var(--bg-color);
    background-image: var(--bg-gradient);
    color: var(--primary-text);
    display: flex;
    justify-content: center;
    align-items: flex-start;
    min-height: 100vh;
    padding: 2rem 1rem;
}
.app-container {
    width: 100%;
    max-width: 700px;
    display: flex;
    flex-direction: column;
    gap: 1.5rem;
    animation: fadeInUp 0.6s 0.2s ease-out forwards;
    opacity: 0;
}
header { text-align: center; }
header h1 {
    font-size: 3rem;
    font-weight: 700;
    color: var(--primary-text);
    text-shadow: 0 0 10px rgba(100, 255, 218, 0.3);
}
.subtitle {
    font-size: 1.1rem;
    color: var(--secondary-text);
    margin-top: -0.25rem;
    margin-bottom: 1.5rem;
}
.mode-switcher { display: flex; justify-content: center; gap: 1rem; }
.mode-switcher button {
    font-family: var(--font-sans);
    font-size: 1rem; padding: 0.75rem 1.5rem; background-color: transparent;
    color: var(--secondary-text); border: 1px solid var(--border-color);
    border-radius: 6px; cursor: pointer; transition: all 0.3s ease;
}
.mode-switcher button:hover {
    background-color: rgba(100, 255, 218, 0.1);
    color: var(--accent-color);
}
.mode-switcher button.active {
    background-color: var(--accent-color); color: var(--bg-color);
    font-weight: 600; border-color: var(--accent-color);
}
.score-container { text-align: center; font-size: 1.2rem; color: var(--secondary-text); }
.score-container span {
    color: var(--primary-text); font-weight: 600; transition: color 0.3s ease;
    display: inline-block;
}
.score-container span.pulse { animation: scorePulse 0.5s ease-in-out; }
.score-container span.correct { color: var(--correct-color); text-shadow: 0 0 8px var(--correct-glow); }
.score-container span.incorrect { color: var(--incorrect-color); text-shadow: 0 0 8px var(--incorrect-glow); }

.feedback-container { min-height: 50px; display: flex; justify-content: center; align-items: center; }
#feedback-message {
    padding: 0.75rem 1.5rem; border-radius: 6px; font-weight: 600;
    opacity: 0; transform: scale(0.9);
}
#feedback-message.visible { animation: feedbackPop 0.4s ease-out forwards; }
#feedback-message.correct {
    background-color: rgba(40, 167, 69, 0.2);
    color: var(--correct-color); border: 1px solid var(--correct-color);
}
#feedback-message.incorrect {
    background-color: rgba(220, 53, 69, 0.2);
    color: var(--incorrect-color); border: 1px solid var(--incorrect-color);
}
.challenge-wrapper { position: relative; }
.challenge-container {
    background-color: var(--card-bg); padding: 2rem;
    border-radius: 8px; border: 1px solid var(--border-color);
    box-shadow: 0 10px 30px -15px rgba(2,12,27,0.7);
    display: flex; flex-direction: column; gap: 1.5rem;
    transition: opacity 0.3s ease, transform 0.3s ease;
}
.challenge-container.anim-out { opacity: 0; transform: translateY(-10px); }
.challenge-container.anim-in { animation: fadeInUp 0.5s ease-out forwards; }
.challenge-container.shake { animation: shake 0.6s cubic-bezier(.36,.07,.19,.97) both; }
.challenge-container h3 { color: var(--primary-text); font-size: 1.5rem; text-align: center; }

.question-prompt {
    font-family: var(--font-mono); font-size: 1.25rem; text-align: center;
    color: var(--primary-text); background-color: var(--bg-color);
    padding: 1rem; border-radius: 4px; word-break: break-all;
    display: flex; flex-direction: column; gap: 1rem; align-items: center;
}
.prompt-group { display: flex; align-items: center; gap: 1rem; flex-wrap: wrap; justify-content: center; }
.prompt-label { font-size: 0.9rem; color: var(--secondary-text); }
.binary-value span { padding: 0.2rem 0.1rem; border-radius: 3px; }
.binary-value .sign-bit { background-color: var(--sign-bit-bg); color: #f78787; }
.binary-value .mantissa-body { background-color: rgba(100, 255, 218, 0.1); color: var(--accent-color); }
.binary-value .exponent-val { background-color: var(--exponent-bg); color: #ffdd87; }
#addition-prompt { align-items: flex-end; }
#addition-prompt .addition-line { width: 100%; border-bottom: 1px solid var(--border-color); margin-left: 3rem; }
#addition-prompt .operator { font-size: 1.5rem; color: var(--secondary-text); margin-right: 1rem; }

form { display: flex; flex-direction: column; gap: 1rem; }
.input-group { display: flex; flex-direction: column; gap: 0.5rem; }
.input-group label { font-size: 0.9rem; color: var(--secondary-text); }
input[type="text"], input[type="number"] {
    width: 100%; padding: 0.75rem; background-color: var(--bg-color);
    border: 1px solid var(--border-color); border-radius: 6px;
    color: var(--primary-text); font-size: 1.1rem; font-family: var(--font-mono);
}
input:focus { outline: none; border-color: var(--accent-color); box-shadow: 0 0 0 3px rgba(100, 255, 218, 0.2); }
.action-buttons { display: flex; gap: 1rem; margin-top: 0.5rem; }
.next-question-btn { flex-grow: 1; }
button {
    font-family: var(--font-sans); font-weight: 600; font-size: 1rem;
    padding: 0.75rem; background-color: var(--accent-color);
    color: var(--bg-color); border: none; border-radius: 6px;
    cursor: pointer; transition: all 0.3s ease;
}
button:hover { filter: brightness(1.1); }
.secondary-btn { background-color: var(--border-color); color: var(--primary-text); }
.secondary-btn:hover { background-color: var(--secondary-text); }
footer { text-align: center; color: var(--secondary-text); font-size: 0.9rem; margin-top: 1rem; }