:root {
    --primary: #2563eb;
    --primary-dark: #1e40af;
    --bg-color: #f3f4f6;
    --card-bg: #ffffff;
    --text-main: #1f2937;
    --text-sub: #6b7280;
    --success: #16a34a;
    --warning: #ca8a04;
    --danger: #dc2626;
}

* {
    box-sizing: border-box;
    -webkit-tap-highlight-color: transparent;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--bg-color);
    color: var(--text-main);
    margin: 0;
    padding: 0;
    height: 100vh;
    display: flex;
    flex-direction: column;
}

/* --- Views --- */
.view {
    display: none;
    flex-direction: column;
    height: 100%;
    padding: 20px;
    overflow-y: auto;
}

.view.active {
    display: flex;
}

/* --- Components --- */
h1,
h2 {
    margin-top: 0;
    text-align: center;
}

.input-group {
    margin-bottom: 15px;
}

label {
    display: block;
    margin-bottom: 5px;
    font-weight: 500;
    color: var(--text-sub);
}

input[type="text"],
input[type="password"],
input[type="url"] {
    width: 100%;
    padding: 12px;
    border: 1px solid #d1d5db;
    border-radius: 8px;
    font-size: 16px;
    /* Prevents iOS zoom */
}

button {
    width: 100%;
    padding: 14px;
    border: none;
    border-radius: 12px;
    font-size: 16px;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.1s, opacity 0.2s;
    margin-bottom: 10px;
}

button:active {
    transform: scale(0.98);
}

.btn-primary {
    background-color: var(--primary);
    color: white;
}

.btn-secondary {
    background-color: #e5e7eb;
    color: var(--text-main);
}

.btn-success {
    background-color: var(--success);
    color: white;
}

.btn-warning {
    background-color: var(--warning);
    color: white;
}

.btn-danger {
    background-color: var(--danger);
    color: white;
}

/* --- Flashcard --- */
.flashcard-container {
    flex-grow: 1;
    display: flex;
    justify-content: center;
    align-items: center;
    perspective: 1000px;
    margin: 20px 0;
}

.flashcard {
    width: 100%;
    max-width: 400px;
    height: 60vh;
    position: relative;
    transform-style: preserve-3d;
    -webkit-transform-style: preserve-3d;
    /* Critical for iOS */
    transition: transform 0.6s;
    cursor: pointer;
}

.flashcard.flipped {
    transform: rotateY(180deg);
    -webkit-transform: rotateY(180deg);
}

.card-face {
    position: absolute;
    width: 100%;
    height: 100%;
    backface-visibility: hidden;
    -webkit-backface-visibility: hidden;
    /* Critical for iOS */
    background: var(--card-bg);
    border-radius: 20px;
    box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    padding: 30px;
    text-align: center;
    /* Ensure no transparency leak */
    z-index: 2;
}

.card-back {
    transform: rotateY(180deg);
    -webkit-transform: rotateY(180deg);
    justify-content: flex-start;
    padding-top: 40px;
    z-index: 1;
    /* Initially behind */
}

/* When flipped, the backface-visibility handles the z-order visual */

.word-orig {
    font-size: 2.5em;
    font-weight: 800;
    color: var(--text-main);
    margin-bottom: 10px;
}

.phonetic {
    color: var(--text-sub);
    font-family: "Courier New", monospace;
    margin-bottom: 20px;
}

.context {
    font-style: italic;
    color: #4b5563;
    line-height: 1.5;
    margin-top: 20px;
}

.meaning {
    font-size: 1.4em;
    color: var(--primary-dark);
    margin: 20px 0;
    font-weight: 600;
}

/* --- Review Actions --- */
.actions-bar {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr 1fr;
    gap: 8px;
    width: 100%;
    margin-top: auto;
    /* Push to bottom of flex container */
    padding-top: 15px;
    border-top: 1px solid #eee;
}

.actions-bar button {
    padding: 10px 0;
    margin-bottom: 5px;
    /* Space for Master row */
    font-size: 0.85em;
    border-radius: 8px;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.1);
}

.card-back {
    /* Ensure content scrolls if too long, but buttons stay visible? 
       Actually, let's make the card scrollable internally if needed */
    overflow-y: auto;
}

/* --- Dashboard Stats --- */
.stats-grid {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 15px;
    margin-bottom: 30px;
}

.stat-card {
    background: white;
    padding: 20px;
    border-radius: 12px;
    text-align: center;
    box-shadow: 0 2px 5px rgba(0, 0, 0, 0.05);
}

.stat-val {
    font-size: 2em;
    font-weight: 800;
    color: var(--primary);
}

.stat-label {
    font-size: 0.9em;
    color: var(--text-sub);
}

/* --- Toast --- */
.toast {
    position: fixed;
    bottom: 30px;
    left: 50%;
    transform: translateX(-50%);
    background: #333;
    color: white;
    padding: 12px 24px;
    border-radius: 50px;
    font-size: 0.9em;
    opacity: 0;
    transition: opacity 0.3s;
    pointer-events: none;
    z-index: 100;
    white-space: nowrap;
}

.toast.show {
    opacity: 1;
}